Search

Due to the limited maximum output power of the pulsers based on avalanche transistors, high-power ultrawideband (UWB) radiation systems usually synthesize plenty of modules simultaneously to achieve a high peak effective potential (rEp). However, this would lead to an increased aperture size as well as a narrower beam, which would limit their applications in intentional electromagnetic interference fields. In this paper, a high-power UWB radiation system with beam broadening capacity is developed. To achieve beam broadening in the time domain, a power-law time delay distribution method is proposed and studied by simulation, and then the relative excitation time delays of the modules are optimized to achieve higher rEp and avoid beam splitting in the beam broadening mode. In order to avoid false triggering of the pulser elements when implementing the beam broadening, the mutual coupling effect in the system is analyzed and suppressed by employing onboard high-pass filters, since the mutual coupling effect is much more severe in the low-frequency range. Finally, a radiation system with 36 modules is developed. Measuring results indicate that in the high-rEp mode, the developed system could achieve a maximum effective potential rEp of 313.6 kV and a maximum pulse-repetition-rate of 20 kHz. In the beam broadening mode, its half-peak-power beam width in the H-plane is broadened from the original value of 3.9° to 7.9°, with a maximum rEp of 272.9 kV. The polarization direction of the system could be flexibly adjusted by a built-in motor. [ABSTRACT FROM AUTHOR]

In this paper, a kind of tightly coupled array (TCA) with time-domain beam scan is developed for the radiation of high-power ultrawideband (UWB) electromagnetic pulses, and the peak-power pattern is proposed to characterize the directivity. First, the active voltage standing wave ratio (AVSWR) bandwidth of the TCA is optimized, which is the precondition for the beam scan. It indicates that the lower-cutoff frequency (LCF) is inversely proportional to the total length of the whole array; an increase in the distance between the array and the ground plane could remarkably reduce the LCF; and an increase in the element number can also decrease the LCF because of the increase in length, but more elements would make the center elements difficult to match in the low-frequency range, so there is a limitation on the number of elements for a certain LCF. Based on these results, a six-element linear array is designed. Then, the definition of the peak-power pattern is proposed to characterize the directivity of the UWB pulsed antenna. Finally, the optimized six-element array is developed, and the measured working band is 276 MHz–6.4 GHz (AVSWR < 3). The effective potential gain is 1.76, and it improves by 51.7% with a reduction in the aperture area by 68.4% compared with the previous TCA, which means that the aperture efficiency is remarkably improved. The half-power beam width of the developed TCA with the scan angle of 0° is 45°. The time-domain beam scan could be performed with time-delay feeding lines, and the maximum scan angle is over ±30° in the E-plane. The developed TCA can be applied for the generation of high-power electromagnetic environments for the study of intentional electromagnetic interference. [ABSTRACT FROM AUTHOR]

Array antenna is of great significance in realizing the Sub‐6 GHz fifth‐generation (5G) mobile communication systems, however, its utilization in the base station systems implementation is limited due to high power consumption. In this paper, a high radiation efficiency 4 × 4 cylindrical dielectric resonator antenna (CDRA) array fabricated using the temperature stable 0.8Zn2SiO4‐0.2TiO2 composite ceramic is proposed. TiO2‐doped Zn2SiO4 composite ceramics are synthesized by the conventional solid‐state method. Notably, 0.8Zn2SiO4‐0.2TiO2 composite ceramic sintered at 1250 °C demonstrates excellent microwave dielectric properties with dielectric constant (εr ≈ 8.24), high‐quality factor (Q × f ≈ 35 000@8.08GHz), and the temperature coefficient of resonant frequency (TCF ≈ +4.6 ppm °C−1). Moreover, the composite ceramic CDRA array is designed by exciting fundamental HE11δ mode using the aperture coupling microstrip feeding network. The fabricated composite ceramic based 4 × 4 CDRA array has enhanced measured radiation efficiency of up to 87%, high gain of 17.85 dBi and is a promising candidate for utilization in Sub‐6 GHz 5G Base Station communications systems. [ABSTRACT FROM AUTHOR]

In many fields, e.g., ground-penetrating radar and ultra-wideband radiation, a high-pulse-repetition-frequency (PRF) and high-time-base-stability sub-nanosecond pulser is required, and its output waveform should be close to a gaussian pulse. In this article, the transistorized pulser is studied and optimized to improve its output parameters. The printed circuit board circuit parameters of the pulser are first optimized, which is beneficial for the amplitude and the rise time. To improve the time base stability, the collector voltage ramp triggering mode is adopted to replace the conventional base triggering mode for the pulser. For higher PRF, the pulser with the capacitance–transistor parallel structure is immersed in the fluorinert liquid. Moreover, the deficit-charge method is adopted, and small charging capacitances are used in the last few stages to weaken the oscillation in the pulse falling edge. From experimental results, the amplitude of the optimized pulser is 1.35 kV, its rise time is reduced from about 200 to 135 ps, the maximum PRF is improved from 250 to 500 kHz, the pulse jitter is reduced to 22 ps, and the pulse drift is reduced from hundreds of ps/min to 47 ps/min. Meanwhile, the oscillation in its falling edge is greatly suppressed. [ABSTRACT FROM AUTHOR]

In this communication, a time-frequency joint method is proposed to evaluate the performance of ultrawideband (UWB) antennas for the radiation of high-power (HP) electromagnetic pulses. First, conventional antenna parameters, such as the efficiency, gain, and so on, are translated to UWB pulsed antennas from the energy perspective, so as to get several scalar antenna parameters, since energy in one pulse is finite. Thus, the power-spectrum weighted efficiency ($\eta _{e}$), directivity ($D_{e}$), and gain ($G_{e}$) are proposed. Then, several electromagnetic norms of the radiating pulse are selected to characterize the sensitive parameters of the equipment under test (EUT). Based on these, several other scalar antenna parameters are proposed, which are the effective potential gain ($G_{ep}$), pulse sharpening factor (PSF), and peaking impulse gain ($G_{PI}$). Thus, a set of time-domain scalar criteria are proposed to evaluate the performance of HP-UWB antennas. These criteria can be calculated with the frequency functions of conventional antenna parameters, which demonstrate the inherent properties of one antenna. Finally, the performance of two kinds of typical HP-UWB antennas, namely the impulse radiating antenna and the combined antenna, is measured and compared with the proposed method. It indicates that, with the proposed method, one can not only get the inherent properties of one antenna in the frequency domain but also quantitatively compare the performance of different antennas with a given exciting pulse in the time domain with the proposed scalar antenna parameters. [ABSTRACT FROM AUTHOR]

An exponential spacing and sinusoidal folded helical (ESSFH) antenna backed with a cavity is developed in this paper. Compared with the conventional helical (CH) antenna, the proposed antenna not only has smaller dimension but also exhibits a wider working bandwidth, a higher gain, and a better circular polarization (CP) characteristic. To reduce the dimension of the helical antenna, a sinusoidal structure is adopted along the circumference of the helix. However, it deteriorates the CP characteristic of the antenna. Therefore, the structure of the exponential helix spacing is introduced into the sinusoidal folded helical (SFH) antenna. Then, to further improve the gain of the ESSFH antenna, its ground plane is replaced by an optimized cavity. Compared with the CH antenna, the helix diameter of the ESSFH antenna Dλ is reduced from 0.32 to 0.23, and its volume is reduced to 53%. The ESSFH antenna backed with a cavity has an impedance bandwidth of 0.43–1.02 GHz, which is much wider than 0.48–0.60 GHz of the CH antenna. Moreover, it has an axial ratio of 1.77, while the axial ratio of the CH antenna is 2.61. In addition, its effective potential gain is 0.56, which is 22% higher than that of the CH antenna. [ABSTRACT FROM AUTHOR]

In this paper, a high-power ultra-wideband radiation system, composed of multiply radiation modules, is developed based on the space-synthesis method. The radiation module mainly consists of a transistorized pulser, a 2 × 2 combined antenna array, and a power divider. To improve the out parameters [the amplitude, the pulse repetition frequency (PRF), and the rise time] of the transistorized pulser based on the Marx circuit, the influence of the traveling wave process on the output pulse must be concerned. Based on the theoretical analysis, the printed circuit board circuit parameters and the circuit structure of the pulser are optimized. To improve the power synthesis efficiency, the pulse jitter characteristic of the pulser is improved by replacing the conventional base triggering mode with the collector voltage ramp triggering mode for the first-stage avalanche transistor in the pulser. The previous optimized antenna array is utilized in this radiation system, which has a better radiation performance in the prescribed aperture area. In addition, based on the gradient microstrip structure, the power divider integrated with the pulser is designed, which has the advantages of wide bandwidth, low loss, and light weight. Experimental results show that the peak effective potential rEp of the radiation system of 20 radiation modules is 221.8 kV, the maximum PRF could reach 10 kHz, and the half-power radiation angles of its radiation field are about 5° in both the E plane and the H plane. More radiation modules could be integrated into the system to achieve a higher electric field in the future. [ABSTRACT FROM AUTHOR]

Microwave dielectric ceramics are considered to be one of the key materials for dielectric resonators (DR) and have very broad application prospects in the fifth generation (5G) mobile communication system. Here we have prepared high‐quality factor Y3Al5O12 (YAG) transparent dielectric ceramics using high‐purity α‐Al2O3 and Y2O3 powders by cold isostatic pressing of the vacuum sintered with tungsten meshes as the heating elements. Optimum relative permittivity (εr) ~10.53, quality factor Q × f (Q = 1/dielectric loss, f = resonant frequency) ~95, 270 GHz (at =7.37 GHz), and temperature coefficient of resonant frequency (TCF) ~ −51.7 ppm °C−1 were obtained at a sintering temperature of 1780°C for 12 h. For the first time, YAG transparent ceramic dielectric resonator antenna (DRA) is designed as a dominant TE111y mode and a higher‐order TE113y mode using the aperture coupling feeding configuration excitation. The proposed transparent dielectric ceramic DRA can provide a broad impedance bandwidth of 4.193 GHz (ranging from 21.90 to 26.09 GHz) for S11 < −10 dB, radiation efficiency of 92.1%, and compact DR unit. The proposed DRA can be used potentially as a 5G millimeter (mm)‐wave multiple‐input‐multiple‐output (MIMO) antenna unit. [ABSTRACT FROM AUTHOR]

In this article, a Narrow-Width Combined Antenna (NWCA) is proposed for the compact design of high-power ultra-wideband (UWB) systems. The dependence of performances on three dimensions of the combined antenna is investigated so as to minimize its size with a given excitation. It indicates that the working process of the combined antenna can be divided into two stages: (1) energy transmitted from the feeding point to the aperture by the TEM horn structure, and during this stage, the passband is determined by the effect of the impedance taper, which is related to the length and aperture impedance of the antenna, and (2) energy radiated to the free space from the aperture, during which the height of the aperture is the dominant factor. Therefore, the three dimensions of the combined antenna can be appropriately adjusted to make the antenna more compact. Thus, the NWCA is designed by reducing the width and making a slight compensation in height and/or length. Compared with the conventional cubic antenna, the aperture area of the developed NWCA is reduced by 47%, whereas the amplitude of the radiating field only reduces by 2.5% with the given pulsed excitation at the cost of a slight decrease in the pulse duration. It demonstrates that the NWCA is an effectively compact design for the combined antenna in the application of the radiation of the high-power UWB pulse. [ABSTRACT FROM AUTHOR]

Thermoelectric materials are critical parts in thermal electric devices. Here, Zintl phase BaAgSb in space group of P63/mmc is reported as a promising thermoelectric material in density function theory. The anisotropic lattice thermal conductivity and phonon transport properties are investigated in theory. The strong phonon-phonon scattering in BaAgSb exhibits ultra-low lattice thermal conductivity of 0.59 W⋅m−1⋅K−1 along c-axis at 800 K, and high thermoelectric performance ZT = 0.94 at 400 K. The mix of covalent and ionic bond supports high carrier mobility and low thermal conductivity. The unusual features make BaAgSb a potential thermoelectric material. [ABSTRACT FROM AUTHOR]

In this Note, a type of Differential Switched Oscillator (DSWO) system is developed and compared with the conventional single-ended switched oscillator; the power capacity of the DSWO is twice with the same insulation level and twice total length. The DSWO system consists of a differential high-voltage pulsed source, a DSWO, and a pair of differential helical antennas. The differential pulsed source is based on the hydrogen thyratron and pulsed transformer whose peak voltage can theoretically reach ±100 kV to break down the high-pressure switch, whose limiting gas pressure is 25 atm; the DSWO is designed to generate a damped oscillation pulse with a central frequency of 300 MHz, which is also the central frequency of the differential helical antennas. Thus, a damped oscillation pulse can be produced and radiated to generate high-power mesoband circularly polarized electromagnetic fields, and the axial ratio is 1.98. According to the measured results, the central frequency of the developed DSWO is 284 MHz, the percent bandwidth of the radiating field is 11%, and the amplitude of the far-field effective potential is 105 kV. [ABSTRACT FROM AUTHOR]

A transient electromagnetic disturbance (TED) testing system with an adjustable direction of polarization is developed in terms of a low-frequency-compensated symmetric transverse electromagnetic (TEM) horn antenna in this paper. TEM horn antennas are deficient in the low-frequency radiation, which would lead to a very narrow pulse width and cannot be directly applied in radiation tests of TED, especially the TED with abundant low-frequency components such as fast transient overvoltage and high-altitude electromagnetic pulse. To address this problem, a theoretical radiation model and a design principle of the back-loading method are proposed to compensate for the low-frequency performance. After the optimization of the structure according to the simulated results, a TED testing system with the aperture width of 0.9 m and the length of 1.8 m is built. The rise time of the electric field measured at the center of the aperture is 2.39 ns, the pulse width is 27.65 ns, and the peak field is over 50 kV/m, which can meet the requirements of relative standards. The dimension of the working volume is estimated as 0.4 × 0.5 × 0.5 m3 according to the field distribution. [ABSTRACT FROM AUTHOR]

Output power of a transistorized pulser is usually limited by the power capacity of avalanche transistors. To improve the total output power, the power synthesis method is widely used, in which a single pulser with high output power and high time base stability is required. However, the time base stability tends to deteriorate as the output power increases. To improve the output power under the premise of high time base stability, from the perspective of carrier movement, the mechanisms of pulse jitter and pulse drift are investigated. It is found that the pulse jitter is caused by time dispersion of the ionization process in the collector depletion region, while the pulse drift is due to the decrement of the diffusion coefficient Dn and the electron mobility μn, which are both temperature-dependent. Based on the microscopic theoretical study, some macroscopic improvements on the time base stability are made. Some parameters of the trigger pulse and the circuit (e.g., charging capacitance) are optimized experimentally. Consequently, we achieved a pulser with an amplitude of 1.8 kV, pulse jitter of 25 ps, pulse drift of 100 ps/min at a pulse repetition frequency (PRF) of 100 kHz. Additionally, a new parameter k, the product of the highest PRF f and the peak power Ep, is defined to evaluate the output power. With almost the same time base stability, the proposed pulser has a k of 6.48 GHz W, which is improved significantly. Finally, a synthesized pulser with an amplitude of 2.5 kV and highest PRF of 100 kHz is achieved. [ABSTRACT FROM AUTHOR]

The traveling-wave Marx generator was first proposed by Carl Baum to analyze the switch-closure propagation process in fast pulsed-power systems. To improve the performance of the transistorized sub-nanosecond pulse generator, the traveling-wave Marx circuit with inter-stage transmission lines is studied. Simulations indicate that the delay time and the impedance of inter-stage transmission lines [microstrip lines on printed circuit board (PCB)] are main factors affecting the pulse waveform. Based on it, the series connection of modularized Marx circuits is proposed, which has the advantages of adjustable amplitude and bendable circuit layout. A compact high-amplitude pulse generator is developed with the amplitude of 8.2 kV, the rise time of 150 ps, and the PCB length of 35 cm. For higher pulse repetition rate, the heat dissipation design of PCB is necessary; however, due to the variations in the microstrip line structure, the commonly used metallic heat sink may cause a significant decrease in pulse amplitude. Thus, a novel heat dissipation design is proposed by optimizing the layout of metallic sinks and introducing heat-conducting ceramic sinks. A high-repetition-rate pulse generator is developed with the maximum pulse repetition rate of 600 kHz, the amplitude of 1.1 kV, and the rise time of 160 ps. [ABSTRACT FROM AUTHOR]

In this paper, the combined antenna array is developed to maximize the effective potential gain ($G_{ep}$) within finite aperture area for the high-power ultra-wideband (UWB) radiation. The idea is to make the antenna element as small as possible, so that more elements can be arranged within the prescribed aperture area to maximize $G_{ep}$ of the UWB system. On the other hand, the antenna element should match the pulse excitation. This means that in the frequency domain, the working band of the antenna element should cover the spectrum of the radiated pulse, and in the time domain, critical parameters of the radiated field (e.g., rise time of the monopolar pulse) should not be distorted, and those can be the principles for the UWB antenna to match the pulsed excitation, based on which the minimum size of the antenna element can be determined. With this method, a four-element combined antenna array is designed. Also, an impedance transformer and power divider are designed to feed the antenna array. Also, a big combined antenna is developed with the same aperture dimensions (30 cm $\times30$ cm) as the antenna array. Then, the performances of the antenna array and the big antenna are measured and compared. Compared with the big antenna, $G_{ep}$ of the antenna array is 21% higher under the applied excitation, which indicates that the proposed method can significantly improve $G_{ep}$ of the UWB system within the prescribed aperture area. Finally, the antenna array is furthermore optimized by adjusting the distances between the elements, and $G_{ep}$ is improved by another 11%, the total improvement is 33%, and the corresponding effective potential gain is 1.49. [ABSTRACT FROM AUTHOR]

In this letter, a wearable all-textile metasurface antenna (MSA) for 5 GHz wireless body area network (WBAN) applications is proposed. All the components of the proposed MSA are made of the comfort textile materials. A metasurface with high permittivity values is placed right above a wide-bandwidth planar inverted-F antenna to realize size miniaturization and gain enhancement. The proposed MSA has a profile of 4 mm (0.07λ0) and occupies an area of 42 mm × 28 mm (0.77λ0 × 0.51λ0). Moreover, this antenna realizes a measured peak gain of 6.70 dBi, an average efficiency of 77%, and an operating band from 4.96 to 5.90 GHz that covers the 5 GHz WBAN band. In addition, the on-body studies show that the MSA is suitable for wearable applications. [ABSTRACT FROM AUTHOR]

In this letter, a high-gain and low-profile quasi-Cassegrain antenna based on metasurfaces (MS) is proposed. Thanks to the structure of the dual reflectors and the phase compensation technology achieved by MS, the proposed antenna presents a balance between high gain and low profile. This antenna achieves the peak gain of 13.7 dBi, sidelobe level less than −19 dB, and half-power beamwidth of 38° (H-plane) and 28° (E-plane). At the same time, it has a low profile of 12.6 mm (0.244λ0) and occupies an area of 132 mm × 132 mm (2.55λ0 × 2.55 λ0). The proposed quasi-Cassegrain antenna in this letter provides an alternative for the high-gain and low-profile antenna and also enriches the applications of MS in the microwave band. [ABSTRACT FROM AUTHOR]

Transient electromagnetic fields can couple to overhead power transmission and distribution lines, causing damage to the connected equipment. In real cases, incident electromagnetic fields exhibit different spatial and temporal waveform distributions along the line. Normally, to ensure the accuracy of the simulation results, a large number of observation points are needed along the line, which is difficult to obtain. This paper proposes a new approach to address this problem. The proposed approach is based on Agrawal et al.’s coupling model, in which the amplitude and phase distributions of the horizontal exciting electric field along the line are, respectively, represented by the Fourier series and polynomial functions in the frequency domain using two kinds of least squares methods. As a result, the source terms along the line can be accurately evaluated starting from a limited number of observation points. The proposed approach has been validated experimentally. [ABSTRACT FROM AUTHOR]

A wearable circular ring slot antenna with electromagnetic bandgap (EBG) structure for wireless body area network application is proposed in this letter. According to the analysis of equivalent circuit model, the volume of the EBG element is miniaturized for wearable applications. The measured impedance bandwidth of the proposed antenna is observed to be 2.28–2.64 GHz, which covers the 2.4 GHz Industrial Scientific Medical (ISM) band. The measured half-power beamwidths are 60° and 54° in the H-plane and the E-plane, respectively, and the front-to-back ratios are 17 and 13 dB in the H-plane and the E -plane, respectively. The specific absorption rate calculated values for tissue in 1 g (for the U.S. standard) and 10 g (for Europe standard) are both less than the limitations. In conclusion, it is proper to use the proposed antenna in wearable applications. [ABSTRACT FROM AUTHOR]

In this note, a portable ultrawideband (UWB) electromagnetic radiator is developed based on a transistorized pulser with the peak power of 1.4 MW, the rise time less than 150 ps, and the repetition frequency of 50 kHz. To generate high-amplitude pulses, a 100-stage Marx circuit with parallel connection of multiple transistors is proposed. To improve the pulse repetition rate, the parallel charging Marx circuit is adopted with ferrite beads connected in series between stages for high isolation of pulses. In order to radiate the UWB electromagnetic pulse directionally, a compact combined antenna array is fabricated and connected with the pulser via a coaxial feeding module. The effective potential of the UWB radiator reaches 10.5 kV with the band range (−10 dB) from 173 MHz to 2.32 GHz. [ABSTRACT FROM AUTHOR]

In the synthetic test of high-voltage circuit breakers, insulation failures occur very often when the breaker operates frequently. It is very important to diagnose the early insulation fault of the breaker in the synthetic test. However, the installed voltage and current sensors of the synthetic test circuit are designed to measure the low-frequency components, such as the power frequency voltage and current. It is difficult to detect the high-frequency partial discharge caused by the breaker's insulation fault. The partial discharge can generate a radiated electromagnetic pulse. Even the weak partial discharge, which causes a small change in the voltage and current, can generate a large electromagnetic pulse, because of the large rate of change of the voltage and current. So the breaker's insulation status can be assessed by the E-field (electric field) pulses measurement. First, a portable measurement system is developed to measure the transient E-field produced by the breaker's switching operation. The wide frequency response band and large measurement range of this system guarantee the accuracy of the pulse measurement. Then, the test results show that the working process of the synthetic test circuit can be reflected by its corresponding transient E-field pulses. By analyzing the waveform characteristics of the E-field pulses of the synthetic test, the partial discharge caused by the breaker insulation fault can be distinguished. [ABSTRACT FROM PUBLISHER]

• A novel application of 2D material Ti 2 B is proposed with high Li/Na storage capacity and extremely low diffusion barrier. • The invisible variation of electron density of states and volume indicates the stability of battery performance. • No-ignorable influence of magnetic in battery performance is analyzed. Based on the theoretic analysis of Ti 2 B monolayer by first-principles calculations, we find that the Ti 2 B monolayer is one of the promising candidates for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) electrode materials. In comparison with other materials, Ti 2 B monolayer exhibits relatively high capacity (503.1 mA h g−1) and low diffusion barriers (17.2–23.5 meV). During the ion insertion/retraction, extremely high structure stability is indicated by the nearly invisible volumetric variation, and steady metallic character is manifested by the abundant electrons near the Fermi level. In the ground state of ferromagnetism, the magnetic effects are revealed on the thermal stability, charge transfer, ions diffusion, operating voltage and storage capacity. [ABSTRACT FROM AUTHOR]

Nanocomposite membranes are strongly desired to break a trade-off between permeability and selectivity. This work reports new thin film nanocomposite (TFN) forward osmosis (FO) membranes by embedding aluminosilicate nanotubes (ANTs) into a polyamide (PA) rejection layer. The surface morphology and structure of the TFN FO membranes were carefully characterized by FTIR, XPS, FESEM and AFM. The ANTs incorporated PA rejection layers exhibited many open and broad "leaf-like" folds with "ridge-and-valley" structures, high surface roughness and relatively low cross-linking degree. Compared with thin film composite (TFC) membrane without ANTs, the TFN membrane with only 0.2 w/v% ANTs loading presented significantly improved FO water permeability, selectivity and reduced structural parameters. This promising performance can be mainly contributed to the special ANTs embedded PA rejection layer, where water molecules preferentially transport through the nanochannels of ANTs. Molecular dynamic simulation further proved that water molecules have much larger flux through the nanotubes of ANTs than sodium and chloride ions, which are attributed to the intrinsic hydrophilicity of ANTs and low external force for water transport. This work shows that these TFN FO membranes with ANTs decorated PA layer are promising in desalination applications due to their simultaneously enhanced permeability and selectivity. [ABSTRACT FROM AUTHOR]

Abstract: Tunable full color emissive LiSr3.99−x Dy0.01(BO3)3:xEu3+ (0≤x≤0.09) phosphors peaked at 481nm (blue), 574nm (yellow), 592nm (orange), and 617nm (red) were synthesized in air by high temperature solid-state reaction route. The as-synthesized phosphors were characterized by X-ray powder diffraction (XRD), photoluminescence excitation (PLE) and photoluminescence (PL) spectra. The PLE spectra in the range from 200 to 500nm include an Eu–O charge transfer band (CTB) and several 4f–4f transition peaks of Dy3+ and Eu3+, indicating its potential application in white light emitting diodes (LEDs). The effect of Eu3+ concentration on the emission intensity of LiSr3.99−x Dy0.01(BO3)3:xEu3+ phosphors was investigated in detail and the optical concentration is found to be x=0.005. The CIE chromaticity coordinates for LiSr3.99−x Dy0.01(BO3)3:xEu3+ phosphors are simulated. With an increase in Eu3+ ion concentration, the chromaticity color coordinates can be tuned efficiently from the border of greenish white region to its equal-energy white light point, and eventually to red region. All the results imply that the studied LiSr3.99−x Dy0.01(BO3)3:xEu3+ phosphors could be potentially used as white LEDs. [Copyright &y& Elsevier]

Soil salinity significantly limits rice productivity, but it is poorly understood how excess sodium (Na + ) is delivered to the grains at the reproductive stage. Here, we functionally characterized OsHAK4, a member of the clade IV HAK/KUP/KT transporter subfamily in rice. OsHAK4 was localized to the plasma membrane and exhibited influx transport activity for Na + , but not for K + . Analysis of organ- and growth stage-dependent expression patterns showed that very low expression levels of OsHAK4 were detected at the vegetative growth stage, but its high expression in uppermost node I, peduncle, and rachis was found at the reproductive stage. Immunostaining indicated OsHAK4 localization in the phloem region of node I, peduncle, and rachis. Knockout of OsHAK4 did not affect the growth and Na + accumulation at the vegetative stage. However, at the reproductive stage, the hak4 mutants accumulated higher Na + in the peduncle, rachis, husk, and brown rice compared to the wild-type rice. Element imaging revealed higher Na + accumulation at the phloem region of the peduncle in the mutants. These results indicate that OsHAK4 plays a crucial role in retrieving Na + from the phloem in the upper nodes, peduncle, and rachis, thereby preventing Na + distribution to the grains at the reproductive stage of rice., (© 2024 The Author(s). The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.)

AKT2 potassium (K+) channels are members of the plant Shaker family which mediate dual-directional K+ transport with weak voltage-dependency. Here we show that OsAKT2 of rice (Oryza sativa) functions mainly as an inward rectifier with strong voltage-dependency and acutely suppressed outward activity. This is attributed to the presence of a unique K191 residue in the S4 domain. The typical bi-directional leak-like property was restored by a single K191R mutation, indicating that this functional distinction is an intrinsic characteristic of OsAKT2. Furthermore, the opposite R195K mutation of AtAKT2 changed the channel to an inward-rectifier similar to OsAKT2. OsAKT2 was modulated by OsCBL1/OsCIPK23, evoking the outward activity and diminishing the inward current. The physiological relevance in relation to the rectification diversity of OsAKT2 was addressed by functional assembly in the Arabidopsis (Arabidopsis thaliana) akt2 mutant. Overexpression (OE) of OsAKT2 complemented the K+ deficiency in the phloem sap and leaves of the mutant plants but did not significantly contribute to the transport of sugars. However, the expression of OsAKT2-K191R overcame both the shortage of phloem K+ and sucrose of the akt2 mutant, which was comparable to the effects of the OE of AtAKT2, while the expression of the inward mutation AtAKT2-R195K resembled the effects of OsAKT2. Additionally, OE of OsAKT2 ameliorated the salt tolerance of Arabidopsis., (© The Author(s) 2021. Published by Oxford University Press on behalf of American Society of Plant Biologists.)