The rectification control and physiological relevance of potassium channel OsAKT2.

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.

[Design and Fabrication of Silver Nanoparticles/Graphen Complex Substrate and Its Application for Detecting Uranium (â ¥)].

Uranium is one of the important nuclear materials to nuclear industry. Because of the direct disposal of spent fuel, there is still a huge possibility that uranium migrates into the groundwater, causing water contamination. It is of great importance to understand the concentration and their species distribution in aqueous solutions. Surface-Enhanced Raman Scattering (SERS) technique has been widely used for the detection of uranium (Ⅵ). However, the interactions between uranium (Ⅵ) and SERS substrate cause the symmetric stretching vibration peak of uranium (Ⅵ) shift to low wave number direction, which is unfavorable for confirming the species of uranium (Ⅵ) in aqueous solution. For instance, the normal Raman bands of uranyl in nitric acid solution are 871 cm-1, which belongs to the symmetric stretching mode of UO2+2. However, it moves to 710 cm-1 on the surface of silver nanorods SERS substrtate. What's more, different SERS substrate causes different number of shift. Graphene has advantages of inertness and integrity as well as 2-dimensional thickness. In this paper, graphene-isolated SERS substrate which is silver nanoparticles (AgNPs)/graphene complex substrate, was designed to prevent the interaction between SERS substrate and it was analyzed by using the inert graphene layer. First of all, according to our previous work, AgNPs SERS substrate was fabricated on silicon wafer by using an ascorbic acid-actived self-assembly method. Then, AgNPs/graphene complex substrate was prepared by transfering monolayer graphene onto the self-assembly AgNPs substrate. The morphology of complex substrate was obtained by SEM. Some AgNPs link together closely to form nanochain structures. Nanochain structures were distributed evenly on the surface of silicon wafer. The 2-dimensional thickness of graphene did not affect the morphology of AgNPs. When using the complex substrate to detect uranyl nitrate (5×10-4 mol·L-1)，the Raman peak that appeared around 771 cm-1 is considered to be the symmetric stretching mode of UO2+2, shifting back about 52 cm-1 to high wave number direction when compared with AgNPs substrate, which was about ~719 cm-1. The result indicates that graphene layer isolates the interaction between AgNPs substrate and uranyl in some degree.

Tightly coupled arrays with time-domain beam scan for the radiation of high-power ultrawideband electromagnetic pulses.

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.

A miniatured helical antenna based on the sinusoidal folding structure with exponential spacing.

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.

A modularized high-power ultra-wideband radiation system based on the space-synthesis method.

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.

A compact narrow-width combined antenna for the radiation of the UWB electromagnetic pulses.

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.

Development of a type of differential switched oscillator system for the radiation of mesoband high-power electromagnetic pulses.

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.

[Simulation on soil moisture and water productivity of apple orchard on the Loess Plateau, Northwest China]. / 黄土高原苹果园土壤水分及水分生产力模拟.

The WinEPIC model was used to simulate the dynamics of soil moisture and water productivity in the deep layer of the dry farm apple orchard of Changwu in the Loess Plateau from 1980 to 2018, aiming to provide a scientific basis for the sustainable development of apple production in the area. The results showed that the average annual yield of apple orchards in Changwu area was 27.37 t·hm-2, the average annual evapotranspiration was 673.66 mm, and the average annual water productivity was 4.07 kg·m-3. The number of water stress days in adult apple trees was mainly affected by rainfall. The average number of stress days in the late stage of apple tree growth was 46.46 d. The soil water content in deep layer began to approach withering humidity as early as 9-year-old apple trees. Water supply in the whole growing season of Changwu area was the dominant factor impacting the yield of orchards. The reduction of effective soil water content in deep soil was the main factor restricting yield enhancement in the middle and late growth stages of apple trees. When there was no sufficient precipitation, apple trees would use soil water from deeper soil layer. Excessive precipitation could not be used by apple trees but could be converted into shallow soil moisture and evaporation if the deep layer had less available water. For the mature apple trees, less than 500 mm or higher than 700 mm of annual water supply would cause a decline in production. For apple orchard at different growth periods, water management strategy should be adjusted according to rainfall conditions in different years. Supplementary irrigation, rainwater retention, covering, and pruning of branches could be used to reduce the unproductive and luxury water consumption of apple trees, delay the appearance of deep dry layer of soil, and avoid the waste of water resources while ensuring the growth of apple trees.

High-Quality-Factor AlON Transparent Ceramics for 5 GHz Wi-Fi Aesthetically Decorative Antennas.

Transparent material has been widely used in product design and has seen a large increase in its use. In this paper, a kind of aesthetically decorative 5 GHz Wi-Fi dielectric resonator antenna (DRA) of aluminum oxynitride (AlON) transparent ceramic has been designed. High-quality-factor AlON transparent dielectric ceramics were fabricated by presintering at 1780 °C and further cold isostatic pressing (CIP) under a 200 MPa argon atmosphere. For a 9.0 mm thick specimen, the in-line light transmittance reached 83%. Optimum dielectric constant (εr = 9.32), quality factor (Qf = 47 960) and temperature coefficient (TCF = -51.7 ppm/°C) was achieved in the AlON transparent ceramic by cold isostatic pressing. As a result, the proposed aesthetically decorative DRA can achieve an impedance bandwidth of 32% (4.48-6.19 GHz), a high radiation efficiency of 85%, and a low cross-polarization discrimination (XPD) of -30 dB. To achieve a broad bandwidth, the proposed antenna was excited in its dominant TE111x mode and higher-order TE113x mode. The proposed antenna is thus an excellent candidate for an indoor decoration Wi-Fi antenna.

A transient electromagnetic disturbance testing system based on low-frequency-compensated symmetric TEM horn antenna.

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.

High power and high pulse repetition frequency transistorized pulser by time base stability improvement and power synthesis technique.

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.

Aluminosilicate Nanotubes Embedded Polyamide Thin Film Nanocomposite Forward Osmosis Membranes with Simultaneous Enhancement of Water Permeability and Selectivity.

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.

A portable ultrawideband electromagnetic radiator with a 1.4 MW/50 kHz solid-state subnanosecond pulser.

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.

[Research Advances on Therapy of Elderly Acute Myeloid Leukemia -Review].

Acute myeloid leukemia is most common in the elderly patients, and the most elderly patients are thought to be unfit for intensive treatment because of the risk of fatal toxicity, and required other therapeutic approaches to optimize clinical outcome for them. Domestic and foreign scholars have carried out a lot of new drugs and treatment programs. This review focuses on the advances of therapy for elderly acute myeloid leukemia, including biological characteristics of elder AML, adoptive immunotherapy, allogeneic hematopoietic stem cell transplantation and so on.

[Efficacy of Nonmyeloablative Allogeneic Hematopoietic Stem Cells for 14 Case of Severe Acquired Aplastic Anemia].

OBJECTIVE: To investigate the therapeutic efficacy of nonmyeloablative allogeneic hematopoietic stem cells transplantation for severe acquired aplastic anemia (SAA). METHODS: Fourteen patients with severe acquired aplastic anemia received nonmyeloablative allogeneic hematopoietic stem cells transplantation from HLA matched sibling donors, among them 8 cases were dagnosed as SAA-I, 6 cases were diagnosed as SAA-II. The conditioning regimen consisted of fludarabine (FIUD), cyclophosphamide (CTX) and anti-thymocyte globulin (ATG/ALG). The prophylaxis for graft-versus-host disease (GVHD) was performed with cyclosporine (CsA) combined with mycophenolate mofetil (MMF) or tacrolimus (FK506). RESULTS: All the patients gained a quick successfully engraftment of donor hametopoietic cells. The mean recovery time for neutrophil and platelet was 9 d and 13 d respectively. All the patients have acquired a full donor chimerism before 14 d. There were only 2 cases of GVHD: one out of them was acute skin GVHD (grade I) at day 70 after transplantation and the other was chronic liver GVHD (grade I) in 1 years after transplantation, the GVHD more than degree II did not coccur in all patients, 9 patients with bacterial and fungal mixed infection and (or) virus infection were observed, and improved after anti-infection therapy. The median follow-up time were 54.5 months (ranged between 5-144 months), and 12 patients remain disease-free survival currently, only 2 patients died of fungal infectin. CONCLUSION: Transplantation of nonmyeloablative allogeneic hematopoietic stem cell is safe and effective for the treatment of severe acquired aplastic, but the prevention, treatment and monitoring of infection need to be enhance.