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The 220-GHz continuous wave (CW) folded waveguide (FWG) traveling wave tube (TWT) is presented as the high-power amplifier for the terahertz (THz) communication system in this article. This tube is designed and fabricated including FWG circuit, electron gun, periodical permanent magnet system, coupling window, and thermal management structure. The test results show that with the pencil beam of 20.5 kV and 52.4 mA, the output power is 16 W and the corresponding bandwidth is 7 GHz from 213 to 220 GHz, and the maximum power and the corresponding gain are 30 W and 31.2 dB at the frequency of 217 GHz.

The preparation of high-efficiency and low-cost electrocatalysts is vital to the development of green hydrogen energy. In this study, 3D NiCu electrodes with hierarchical micro-nano structure was constructed by a simple direct-write 3D printing technology and followed by the treatment of thermal oxidation - electroreduction steps. The composite structure of Cu NWs/Cu2O and Ni/NiO in the prepared 3D NiCu promotes the dissociation of water and the conversion of hydrogen, and the special micro-nano structure displays a large active surface area. Therefore, the 3D NiCu exhibits a low overpotential of 70 mV to deliver a current density of 10 mA cm−2. It demonstrates outstanding stability in the hydrogen evolution reaction experiment for 100 h in 1 M KOH. Overall, this research provides a pioneer of modified 3D printing to hydrogen production by water electrolysis.

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Morphology transition of block copolymer assemblies in response to external stimuli has attracted considerable attention. However, our knowledge about the mechanism of such a transition is still limited, especially for rod-coil block copolymers. Here, we report a programmable morphology evolution of assemblies induced by variation of chain ordering for rod-coil-rod triblock copolymers. A sequence of morphology transition from ellipsoids to disks, bowls, and vesicles is observed by increasing the solution temperature. At high temperatures, the mobility of the rod chain increases and the rigidity of the rod chain decreases. This gives rise to an ellipsoid-to-vesicle morphology transition. Dissipative particle dynamics theoretical simulations were performed to reveal the mechanism of this morphology transition process. It was found that the increase of rod chain mobility and the decrease of rod chain rigidity induce a decrease of chain ordering of rod blocks as temperature increases, which results in an ellipsoid-to-vesicle morphology transition. The gained information can guide the construction of nanoassemblies based on the rod-coil block copolymers.

Aiming to redundant parallel mechanism, on the basis of the kinetic energy method, virtual work principle and perturbation method, the generalized mass matrix and generalized stiffness matrix are obtained, respectively. Two indices on inertial coupling and elastic coupling are defined to measure the decoupling level of the redundant parallel mechanism in terms of two generalized matrices. Furthermore, an algebraic solution method for natural frequency equation of the mechanism is utilized to obtain the natural frequency by means of the Cholesky decomposition method. And then, in order to minimize inertial coupling and elastic coupling, and maximize the natural frequency of the mechanism, two indices and natural frequency are taken as objective functions to optimize the structural parameters of the redundant mechanism, so that optimal dynamic performance of the mechanism is acquired. In the optimization of natural frequency, two optimal solutions are selected. One is to consider inertial coupling and elastic coupling and the other is to ignore inertial coupling and elastic coupling. Finally, the dynamic performance of the two indexes is better by comparing the dexterity of the two solutions

This paper presents a comparative study on the laser-induced ignition and combustion characteristics between nanometer-sized aluminum (nano-Al) and micron-sized aluminum (micro-Al) powder stacks. S...

The electrode erosion and lifetime performance of a compact and repetitively triggered field distortion spark gap switch were studied at a repetitive frequency rate of 30 Hz, a peak current of 8.5 kA, and a working voltage of ±35 kV when the switch was filled with a gas mixture of 30% SF6 and 70% N2 at a pressure of 0.3 MPa. The variations of the time-delay jitter and the self-breakdown voltage were both studied for the whole service lifetime of the spark gap switch. The morphology of both the electrodes and the plate insulator, before and after the service lifetime tests, is also analyzed. The results show that during these tests, the time-delay jitter is basically synchronized with the self-breakdown voltage jitter, and both undergo firstly a process of rapidly decreasing their values, then remaining stable, and finally and gradually increasing after 70 000 pulses. The change in the electrode surface roughness (i.e., surface profile) is caused by erosion and chemical deposits in the switch cavity, which are mainly the two factors that affect the time-delay jitter of the switch. Tip protrusions on the electrode surface, due to electrode erosion, contribute to reducing the time-delay jitter. However, due to chemical reactions, fluorides and sulfides are deposited on the switch components, as well as metal particles caused by electrode erosion sputtering. Slowly, after a large number of shots, all these phenomena affect the self-breakdown performance resulting in an increased self-breakdown voltage jitter, which also causes the time-delay jitter to increase. Although there are a number of reasons that contribute to the deterioration of the performance of the switch, it is fortunate that if a switch suffering a degraded performance is reassembled, with the electrodes mechanically polished and all the components cleaned, the optimal performance of the switch can be restored. If maintenance work is carried out regularly to preserve the condition of the switch’s inner components, the service lifetime of the switch can be prolonged.

In aluminum electrolysis, sodium penetration into carbon cathodes is considered as the main cause of cell failure and efficiency loss, but the detailed mechanism is still not definitely clear. Since the macroscopic properties of material depend on the microscopic structures, a large-scale atomistic model of anthracite cathodes was constructed to represent several important structural characteristics. Combined with Monte Carlo and molecular dynamics simulations, the adsorption and diffusion behaviors of sodium were investigated, respectively. The results suggest that sodium adsorption mainly occurs in the larger micro-pores with the range of 10–19 A, while it accords well with to type-I Langmuir adsorption model. The sodium is found to be preferentially adsorbed in arch-like structures with 5- or 7-membered rings or around heteroatom, especially oxygen. Moreover, the movements of sodium through carbon matrix mainly depend on the continuous diffusive motion while most sodium particles tend to be trapped in voids with small mobility. The calculated transport diffusion coefficient is equal to 6.132 × 10−10 m2/s, which is in outstanding agreement with experimental results. This fundamental research would contribute to the understanding of sodium penetration mechanism and the optimization of cathode industry in the future.

The new phthalideisoquinoline hemiacetal alkaloids (2-7) and the known analogues (1 and 8) were isolated from the bulbs of Corydalis decumbens. The new compounds were characterized by analysis of their NMR spectroscopic data, chemical degradation syntheses, X-ray crystallography, and comparison of experimental and calculated ECD data. All the isolates were screened in vitro for inhibitory activity of spontaneous calcium oscillations in primary cultured neocortical neurons. Compounds 1-3 and 5-7 were found to be active in the suppression of spontaneous calcium oscillations with IC50 values of 6.8, 5.6, 11.6, 10.2, 8.3, and 3.1 μM, respectively. It was also observed that the presence of hydroxy, methoxy, and ethoxy groups at the remote stereogenic center C-7' of some isolated phthalideisoquinoline hemiacetal alkaloids could alter the preferred conformation and invert the sign of optical rotation, rather than this resulting from configurational isomerism at C-1 or C-9, and that the 3J1,9 coupling constants of these analogues varied accordingly. For example, compounds 1 and 6 are levorotatory, despite these molecules having the same carbon skeleton and absolute configuration as (+)-egenine. This emphasizes the potential risk of incorrectly assigning absolute configuration based only on observed coupling constants or optical rotation when comparing the data of new compounds with literature values for known analogues, especially within this class of molecules.

SummaryCreating sufficient and sustained fracture conductivity contributes directly to the success of acid-fracturing treatments. The permeability and mineralogy distributions of formation rocks play significant roles in creating nonuniformly etched surfaces that can withstand high closure stress. Previous studies showed that, depending on the properties of formation rock and acidizing conditions (acid selection, formation temperature, injection rate, and contact time), a wide range of etching patterns (roughness, uniform, channeling) could be created that can dictate the resultant fracture conductivity. Insoluble minerals and their distribution can completely change the outcomes of acid-fracturing treatments. However, most experimental studies use homogeneous rock samples such as Indiana limestone that do not represent the highly heterogeneous features of carbonate rocks. This work studies the effect of heterogeneity and, more importantly, the distribution of insoluble rock on acid-fracture conductivity.In this research, we conducted acid-fracturing experiments using both homogeneous Indiana limestone samples and heterogeneous carbonate rock samples. The Indiana limestone tests served as a baseline. The highly heterogeneous carbonate rock samples contain several types of insoluble minerals such as quartz and various types of clays along sealed natural fractures. These minerals are distributed in the form of streaks correlated against the flow direction, or as smaller nodules. After acidizing the rock samples, these minerals acted as pillars that significantly reduced conductivity-decline rate at high closure stresses. Both X-ray diffraction (XRD) and X-ray fluorescence (XRF) tests were performed to pinpoint the type and location of different minerals on the fracture surfaces. A surface profilometer was also used to correlate conductivity as a function of mineralogy distribution by comparing the surface scans from after the acidizing test to the scans after the conductivity test. Theoretical models considering geostatistical correlation parameters were used to match and understand the experimental results.Results of our study showed that insoluble minerals with higher-strength mechanical properties were not crushed at high-closure stress, resulting in a less-steep conductivity decline with an increasing closure stress. If the acid etching creates enough conductivity, the rock sample can sustain a higher closure stress with a much lower decline rate compared with Indiana limestone samples. Fracture surfaces with insoluble mineral streaks correlated against the flow direction offer the benefit of being able to maintain conductivity at high closure stress, but not necessarily high initial conductivity. Using a fracture-conductivity model with correlation length, we matched the fracture-conductivity behavior for the heterogeneous samples. Fracture surfaces with mineral streaks correlated with the flow direction could increase acid-fracturing conductivity significantly as compared to the case when the streak is correlated against the flow direction.The results of the study show that fracture conductivity can be optimized by taking advantage of the distribution of insoluble minerals along the fracture surface and demonstrate important considerations to make the acid-fracturing treatment successful.

This work was stimulated by the assumption that for a gas-filled spark gap closing switch operating at a high repetition frequency, there is an optimal frequency range in which the time-delay jitter reaches a minimum value. The experiments to test this assumption use an electrically triggered, field-distortion spark gap filled with the SF6/N2 gas mixture. The results show that indeed, the time-delay jitter decreases for a range of frequencies for which the filling gas can substantially restore the interelectrode insulation before increasing at a higher operation frequency. The experimental results demonstrate the correctness of the abovepresented assumption: the time-delay jitter of the field-distortion spark gap has its minimum when the unit operates in the repetition frequency range between 20 and 30 Hz. Since the recovery time depends on the gas species and the gap distance, the optimum operation frequency range should also vary depending on the spark-gap distance and the filling gas properties.

Chlorophenols are extremely toxic to the environment and recalcitrant to biological degradation. Herein chemical degradation of 4-chlorophenol (4-CP) from aqueous solutions by zero-valent aluminum (Al), zero-valent iron (Fe), Al and Fe mixtures (Al/Fe mass ratio 90/10, labeled as Al/Fe10) and Al-Fe alloy (Al/Fe mass ratio 90/10, labeled as Al-Fe10) were investigated. No removal was found for 50 mg·L−1 4-CP under anoxic conditions at initial pH 2.5 during a period of 10 hrs while 56%, 83%, 78% and 99% of 4-CP were removed by Fe, Al, Al/Fe10 and Al-Fe10, respectively under aeration conditions. The removal of 4-CP by Al/Fe10 mixtures was primarily in the Fe mode in the beginning 4 h and then transitioned to the Al mode. The removal of 4-CP by Al-Fe10 alloy was accomplished via two intermediate products, hydroquinone (HQ) and 4-chlorocatechol (4-CC), and it was speculated that reactive oxygen species and hydroxyl radicals (·OH) play an important role in the degradation of 4-CP and that Al-Fe intermetallic compounds might catalyze the reactions. This study demonstrates that alloying Al with Fe offers a promising strategy for developing new materials for water and wastewater remediation.

We propose two terahertz coherent perfect graphene-based absorbers that can simultaneously realize the tunable resonant frequency and absorption. The Fermi energy of graphene, which can be changed by applied electric fields affect the frequency of absorption peaks. By adjusting the phase difference between two interfering beams, the absorption intensity can be controlled. The simulated results indicate that the absorptivity can achieve nearly 100% change and the adjusting range of absorption frequency is up to 16 THz. With the flexible movement of four absorption peaks, the absorption bandwidth over 90% can be extended to 10 THz. What is more, this paper displays the application to photoswitch by phase modulation. In particular, the proposed absorbers are polarization-insensitive and almost omnidirectional. We hope that our results can provide substantial help for the potential applications in the future metamaterial devices.

The severe interface charge recombination caused by the large energy difference between perovskite material and carbon electrode significantly limits the further performance improvement of the all-inorganic perovskite solar cells (PSCs). We apply innovatively multilayer of quaternary Ag-In-Ga-S (AIGS) quantum dots (QDs) with cascade-like valence bands as hole-transport materials to assemble all-inorganic PSCs, and the resultant all-inorganic PSCs exhibit a power conversion efficiency (PCE) of 8.46%, which is enhanced by 20.9% in comparison with 7% for the pristine device. The high performance of the PSCs indicates that sequential layers of AIGS QDs with cascade-like energy levels can facilitate the charge separation, reduce the barrier the holes crossing and suppress the charge recombination. Stack of QDs with cascade-like energy levels provide solution-processed PSCs with a new method to enhance device performance.

This paper describes the development of a small field-distortion spark gap switch. Comprehensive experimental studies made with the switch revealed its self-breakdown characteristics, voltage operating range, time delay and jitter, repetition frequency, and finally the electrode erosion processes and duration of its service lifetime. A series of design improvements were required to be implemented in the switch design. For example, to reduce the structural inductance of the switch and to improve its working characteristics, the main electrode was designed as a circular track structure. Similarly, to increase the operation stability and reduce the self-breakdown probability, the trigger electrode was designed as a disk-like structure. Moreover, to balance the gas pressure in the discharge region and increase the stability during closure, a circular hole was added at the center of the trigger electrode. The compact switch has a small size of only 150 mm $\times42$ mm, a weight of 1.5 kg, and can be successfully operated at a voltage over 110 kV, at a repetition rate between 1 and 50 Hz and having a jitter of less than 4 ns. It was experimentally demonstrated that during normal operation conditions, the switch lifetime exceeds 100 000 shots.

Objective According to theory of Chinese medicine property, the ecological environment shapes properties (natures and flavors) of Chinese materia medica (CMM) and there are close relationships between certain natures and flavors. However, to date these observations have not been validated scientifically in the context of the whole flora of a region. The present study aims to address this gap. Methods We collected geographical distributions of 3637 vascular plant species native to the Xinjiang region of northwest China, of which around 812 are medicinal plants. The CMM property characters of these medicinal plants were also collected. All medicinal plants were then analyzed in the occurrence of their natures (cold, cool, neutral, warm, and hot) and flavors (sweet, bitter, sour, salty, and pungent). Possible correlations between these properties and environmental factors, notably climate, as well as correlations with plant species richness of the wider native flora of Xinjiang were then investigated using permutation test and regression. Results Cold species (38.5%) were more numerous than warm (21.0%) and neutral (22.3%), while bitter species (43.3%) were more numerous than pungent (25.6%), sweet (22.4%) and sour (6.7%) ones. Species with bitter flavor were most commonly also cold (48.6%) in nature, sour flavor usually coincided with cold (44.2%) or cool nature (26.0%), whereas pungent or sweet species tended to be warm (34.4%, 28.4%) or neutral (27.8%, 28.4%). The percentages of species of cold/cool nature, bitter flavor were higher in mountainous regions, and the percentages of warm/neutral and pungent/sweet/sour were higher in basins. The percentages of species of cold/cool, bitter were positively correlated with actual evapotranspiration (AET), and also plant species richness but had a bell-shaped relationship with potential evapotranspiration (PET), whereas the inverse situation was shown for warm/neutral and pungent/sweet/sour species. Conclusion Analysis of the data in Xinjiang region of China supports the qualitative observations concerning natures and flavors in traditional theory of Chinese medicine property. Specifically, (i) certain natures and flavors co-occur more frequently than if randomly distributed; (ii) correlations between proportions of natures and flavors and climatic variables suggest a role for the environment in shaping the properties of CMM.

In this paper, the evolution of microstructure and mechanical properties of Super304H during aging at 650 °C is investigated, and the effect between microstructure evolution and properties change a...

Novel antibacterial drugs that treat multidrug resistant pathogens are in high demand. We have synthesized analogs of solithromycin using Cu(I)-mediated click chemistry. Evaluation of the analogs using Minimum Inhibitory Concentration (MIC) assays against resistant Staphylococcus aureus, Escherichia coli, and multidrug resistant pathogens Enterococcus faecium and Acinetobacter baumannii showed they possess potencies similar to those of solithromycin, thus demonstrating their potential as future therapeutics to combat the existential threat of multidrug resistant pathogens.

Nanostructured Cr2O3 thin films were deposited on silicon (100) and 95% alumina substrates at various substrate temperatures and oxygen flow rates using dual-target reactive high-power impulse magnetron sputtering. Grazing incidence X-ray diffraction analysis revealed that the phase structure of the Cr2O3 films varied with the substrate temperature and oxygen flow rate and that a Cr2O3 film with good crystallinity was produced at 300 °C. X-ray photoelectron spectroscopy analysis indicated that an oxygen flow rate of 5 sccm was suitable for depositing a stoichiometric Cr2O3 film. Scanning electron microscopy analysis revealed that the films prepared at oxygen flow rates of 3–15 sccm exhibited a homogenous and uniform nanocrystalline structure. In addition, all the Cr2O3-modified alumina samples exhibited a secondary electron emission (SEE) yield of 2.3, which was much lower than that of the bare alumina (6.82). The sheet resistivity of the Cr2O3-modified alumina samples increased from 8.6 × 1010 to 6.2 × 1011 Ω/□ upon increasing the oxygen flow rate from 3 to 15 sccm. Thus, the deposition of the Cr2O3 film significantly reduced the SEE yield and sheet resistivity of the alumina substrate. In addition, the surface hold-off voltage of alumina was enhanced by up to 23.7%.

A compact low jitter high power repetitive long-pulse relativistic electron beam source with novel circuit structure and mechanical structure is presented. Based on Marx type circuit and direct-drive idea, the key technologies such as high energy density pulse forming network, repetitive high voltage pulse generator and low jitter electrical trigger technology are developed. The volume and weight of the pulsed electron beam source are reduced remarkably by using two-capacitor pulse forming modules, alternating superposition structure on both sides and high electric field shielding technology. The key technical parameters of the electron beam source design include a peak output voltage 1 MV with peak current 20 kA. The impulse is 180 ns and has a repetition frequency 1 ∼ 50 Hz, however, the output power and repetition frequency are able to be adjusted within a certain operating range. The machine has a total volume of 2.5 m3 and weighs 2.2 tons, making it much more compact than conventional electron beam sources. The experimental results show that when the e-beam source is operated under a single pulse condition, the output voltage, current, and power are 0.98 MV, 19.6 kA, and 19.2 GW, respectively. When the e-beam source has a continuous operating time of 10 s at a repetition frequency of 30 Hz and an output power of 16.7 GW, the voltage fluctuation range is limited to within ± 1.5%, and the current fluctuation range is limited to within ± 2%. The delay time jitter between the trigger pulse and the output pulse is limited less than 6.5 ns standard mean deviation. Statistical distributions of the delay time jitter and current amplitude variation of the 300 pulses are approximately Gaussian. When the cooling system is working, the electron beam source can work continuously for 100 s under the conditions of an output power of 16.7 GW and repetition frequency of 30 Hz, and the system operation is stable and reliable.

The influence of electron beam uniformity on the microwave characteristics of coaxial structure Ka-band RKA output cavity is investigated with particle-in-cell simulations. The electron beam non-uniformity is simulated in four different electron emission models: (1) continuous non-emission area, (2) spaced emission, (3) enhanced emission and (4) current density variation emission. The simulation results with the first emission model shows that the output power of Ka-band RKA decreases as the non-emission area increases, while the continuous non-emission area has little effect on the frequency and pulse width of Ka-band microwave; The simulation results with the second emission model shows that the output power of Ka-band RKA is related to the distribution of Z-component of electric field and excitation electric field strength in the beam-wave interaction gap. The more uniform the distribution of Z-component of electric field is, the greater the output power is. The stronger the excitation electric field is, the greater the output power is; The simulation results with the third emission model shows that the intense current density in local area will cause the reduction of output power. The higher the current density of the enhanced emission area is, the smaller the output power is; The simulation results with the fourth emission model shows that the fluctuation of current density during the steady-state phase will cause the fluctuation of microwave frequency and output power. The fluctuation amplitude of frequency and output power are positively related to the fluctuation amplitude of the current density. The larger the fluctuation amplitude of current density is, the greater the fluctuation amplitude of frequency and output power are. The faster the current density changes, the greater the fluctuation amplitude of frequency and output power are.

Insect cuticular hydrocarbons (CHCs) are organic compounds of the surface lipid layer, which function as a barrier against water loss and xenobiotic penetration, while also serving as chemical signals. Plasticity of CHC profiles can vary depending upon numerous biological and environmental factors. Here, we investigated potential sources of variation in CHC profiles of Nilaparvata lugens, Laodelphax striatellus and Sogatella furcifera, which are considered to be the most important rice pests in Asia. CHC profiles were quantified by GC/MS, and factors associated with variations were explored by conducting principal component analysis (PCA). Transcriptomes were further compared under different environmental conditions. The results demonstrated that CHC profiles differ among three species and change with different developmental stages, sexes, temperature, humidity and host plants. Genes involved in cuticular lipid biosynthesis pathways are modulated, which might explain why CHC profiles vary among species under different environments. Our study illustrates some biological and ecological variations in modifying CHC profiles, and the underlying molecular regulation mechanisms of the planthoppers in coping with changes of environmental conditions, which is of great importance for identifying potential vulnerabilities relating to pest ecology and developing novel pest management strategies.

Hydrogen is becoming important clean energy while zerovalent iron (ZVI) and ferroferric oxide are of great interest to many applications including environmental remediation and chemical catalysis. Here, we report production of hydrogen, zerovalent iron and ferroferric oxide octahedron by etching Al–Fe alloys using NaOH solutions. The rate of hydrogen generation increased with increasing NaOH concentration and the alloy's particle size and decreasing the alloy's Fe concentration. Alkaline etching Al–Fe alloy particles of 425–850 μm produced 19–53 μm ZVI particles, which had paralleled ravines of 0.2–0.3 μm wide on the surface and possessed specific surface areas of 30–70 m2/g. The microscale ZVI was highly active for the removal of a model pollutant acid orange 7 from water. After 3–6 h ageing in the alkaline etching solution, the microscale ZVI particles were transformed to octahedral ferroferric oxide with saturation magnetization of 68.2 emu/g and residual magnetization of 13.2 emu/g and a coercive force of 330 Oe. This study provides a new approach for a facile synthesis of highly active ZVI and octahedral ferroferric oxide along with on-board generation of hydrogen from Al–Fe alloys.

The polarization states of scattered photons can be used to map or image the anisotropic features of a nanostructure. However, the scattering strength depends heavily on the refractivity contrast in the near field under measurement, which limits the imaging sensitivity for viral particles which have little refractivity contrast with their nano-ambientes. In this paper, we show the photon scattering signal strength can be magnified by introducing a more abrupt change of refractivity at the virus particle using antibody-conjugated gold nanoparticles (AuNPs), allowing the presence of such viruses to be detected. Using two different deep learning methods to minimize scattering noise, the photon states scattering signal of a AuNPs ligated virus is enhanced significantly compared to that of a bare virus particle. This is confirmed by Finite Difference Time Domain (FDTD) numerical simulations. The sensitivity of the polarization state scattering spectra from a virus-gold particle doublet is 5.4 times higher than that of a conventional microscope image.

MADS-box genes are involved in various developmental processes including vegetative development, flower architecture, flowering, pollen formation, seed and fruit development. However, the function of most MADS-box genes and their regulation mechanism are still unclear in woody plants compared with model plants. In this study, a MADS-box gene (CiMADS43) was identified in citrus. Phylogenetic and sequence analysis showed that CiMADS43 is a GOA-like Bsister MADS-box gene. It was localized in the nucleus and as a transcriptional activator. Overexpression of CiMADS43 promoted early flowering and leaves curling in transgenic Arabidopsis. Besides, overexpression or knockout of CiMADS43 also showed leaf curl phenotype in citrus similar to that of CiMADS43 overexpressed in Arabidopsis. Protein–protein interaction found that a SEPALLATA (SEP)-like protein (CiAGL9) interacted with CiMADS43 protein. Interestingly, CiAGL9 also can bind to the CiMADS43 promoter and promote its transcription. Expression analysis also showed that these two genes were closely related to seasonal flowering and the development of the leaf in citrus. Our findings revealed the multifunctional roles of CiMADS43 in the vegetative and reproductive development of citrus. These results will facilitate our understanding of the evolution and molecular mechanisms of MADS-box genes in citrus.

Insect cuticular hydrocarbons (CHCs) serve as important intersexual signaling chemicals and generally show variation between the sexes, but little is known about the generation of sexually dimorphic hydrocarbons (SDHCs) in insects. In this study, we report the molecular mechanism and biological significance that underlie the generation of SDHC in the German cockroach Blattella germanica. Sexually mature females possess more C29 CHCs, especially the contact sex pheromone precursor 3,11-DimeC29. RNA interference (RNAi) screen against the fatty acid elongase family members combined with heterologous expression of the genes in yeast revealed that both BgElo12 and BgElo24 were involved in hydrocarbon (HC) production, but BgElo24 is of wide catalytic activities and is able to provide substrates for BgElo12, and only the female-enriched BgElo12 is responsible for sustaining female-specific HC profile. Repressing BgElo12 masculinized the female CHC profile, decreased contact sex pheromone level, and consequently reduced the sexual attractiveness of female cockroaches. Moreover, the asymmetric expression of BgElo12 between the sexes is modulated by sex differentiation cascade. Specifically, male-specific BgDsx represses the transcription of BgElo12 in males, while BgTra is able to remove this effect in females. Our study reveals a novel molecular mechanism responsible for the formation of SDHCs and also provide evidences on shaping of the SDHCs by sexual selection, as females use them to generate high levels of contact sex pheromone., Sexual dimorphism of body waxes is prevalent in insects; this study reveals that the sex-differentiation pathway regulates fatty acid elongation, ensuring production of the sexually dimorphic cuticular hydrocarbons needed for high levels of sex pheromone and sexual attractiveness in female cockroaches.

Water retention is critical for physiological homeostasis and survival in terrestrial insects. While deposition of hydrocarbons on insect cuticles as a key measure for water conservation has been extensively investigated, we know little about other mechanisms for preventing water loss in insects. Here, we report two fatty acid synthetic genes that are independent of hydrocarbon production but crucial for water retention in the German cockroach Blattella germanica (L.). First, an integument enriched fatty acid elongase gene (BgElo1) was identified as a critical gene for desiccation resistance in B. germanica; however, knockdown of BgElo1 surprisingly failed to cause a decline in cuticular lipids. In addition, RNA interference (RNAi)-knockdown of an upstream fatty acid synthase gene (BgFas3) showed a similar phenotype, and transmission electron microscopy analysis revealed that BgFas3- or BgElo1-RNAi did not affect cuticle architecture. Bodyweight loss test showed that repression of BgFas3 and BgElo1 significantly increased the weight loss rate, but the difference disappeared when the respiration was closed by freeze killing the cockroaches. A water immersion test was performed, and we found that BgFas3- and BgElo1-RNAi made it difficult for cockroaches to recover from drowning, which was supported by the upregulation of hypoxia-related genes after a 10-h recovery from drowning. Moreover, a dyeing assay with water-soluble Eosin Y showed that this was caused by the entry of water into the respiratory system. Our research suggests that BgFas3 and BgElo1 are required for both inward and outward waterproofing of the respiratory system. This study benefits the understanding of water retention mechanisms in insects.

The Debye relaxation is the main signal in the dielectric measurements of monoalcohols arising from the hydrogen-bonded superstructures, but its physics remains to be cleared. In this work, a monoalcohol of 4-methyl-2-pentanol is studied using dielectric spectroscopies recorded at high pressures. The dynamic parameters of the Debye and structural relaxations are extracted. The calculation of the Kirkwood factor of the Debye relaxation indicates chain-like H-bond molecular configurations. Remarkably, we found that both ratios of the relaxation strength and relaxation time between the Debye and structural dynamics, Δε D/Δε α and τ D/τ α , decreases upon compression, indicating a positive correlation. This is different from the results reported in primary 2-ethyl-1-hexanol and secondary 4-methyl-3-heptanol, where the two ratios are inversely correlated. The discussion and interpretation of these different results are provided.

Removal of naturally occurring strontium (Sr) from groundwater is vital as excessive exposure may lead to bone growth problems in children. Nanofiltration/reverse osmosis (NF/RO) is commonly used in groundwater treatment due to the high effectiveness and simple maintenance of these pressure driven membrane processes. In this research, a pilot-scale NF/RO system was used to desalinate a natural groundwater sample containing high Sr concentration (10.3 mg/L) and &ldquo, old&rdquo, groundwater organic matter (70.9 mg/L) from Esilalei in northern Tanzania to understand the removal of strontium by NF/RO. The impact of applied pressure (10&ndash, 15 bar) and groundwater pH (3&ndash, 12) on the membrane performance including permeate flux, strontium and total organic carbon (TOC) flux and removal was investigated. Increasing applied pressure was found to enhance the flux by increasing the driving force and enhance Sr and TOC removal by dilution effect (water flux higher than Sr passage). The alkaline pH caused severe flux decline likely due to membrane fouling and scaling, while it slightly enhanced Sr removal of RO membranes, but weakened the TOC removal. In contrast, acidic and neutral pH of groundwater enhanced TOC removal. These findings suggest that appropriately high applied pressure and acidic pH condition of groundwater are recommended to apply to the NF/RO membrane system in groundwater desalination to achieve better membrane performance.

DSRD is a powerful semiconductor opening switch for nanosecond high voltage pulse generation. In this paper, a cascade pulse generator based on two-stage DSRDs was presented and tested on a $50\ \Omega$ load. The dependence of the output parameters on the charging voltage is discussed. The results show that with the increase of the charging voltage, the output voltage rise rate increases, up to 4.33 kV/ns, while the rise time is almost the same ∼1ns. The maximum overvoltage factor is 7.86 obtained under 400 V charging voltage. Repetitive operation of the generator at 500Hz was also carried out. In this condition, the deviation of the output voltage amplitude is less than 0.5%, and the jitter of the whole generator is no more than 130 ps.

The switching characteristics of layered silicon device with p+npn+ structure under zero bias voltage were investigated in this paper. A long base device with 10 mm diameters and 4.3 kV operating voltage was used in the experiments. According to the significant difference in the trigger current, the trigger types are divided into two modes, named strong mode and weak mode respectively. The experiment results show that, in both modes, the device can be switched within 200 ps followed by a residual voltage lower than 100 V, and the delay time of switching increases with the decrease of voltage rise rate $dU/dt$ . In each mode, the dependences of the switching time and residual voltage on the $dU/dt$ are similar to the state of reversely biased device. However, comparing the two modes, due to the earlier collision between the ionization front and extraction front, and subsequently the longer quasi-uniform breakdown region in the n-base, the switching time and residual voltage may be larger than those of the weak mode, although the $dU/dt$ is higher in the strong mode. The results show that, the switching performance of the device under test does not depend monotonously on the $dU/dt$ , which implies a moderate $dU/dt$ may be favorable to the ultra-fast switching for a long base and low bias four-layer device.

The dielectric spectra of methyl m-toluate (MMT) in supercooled liquid and glassy states were measured over wide ranges of temperature T at ambient and elevated pressures P. We found that the frequency dispersion of the loss peak contributed by the structural α-relaxation is invariant to changes of P and T, while keeping the loss peak frequency fα(T,P) constant. This isochronal superposition property of the α-relaxation holds for different choices of fα(T,P). The invariant frequency dispersions for the same fα(T,P) are also indicated by the fractional exponent βKWW in the Fourier transform of the Kohlrausch-Williams-Watts (KWW) function. Similarly, the fragility m index of MMT keeps approximately constant on varying pressure, largely different from H-bonded glass formers. The secondary β-relaxation at a frequency higher than fα(T,P) is found to shift to lower frequencies by elevating pressure in concert with the α-relaxation. The ratio τα(T,P)/τβ(T,P) is approximately unchanged to variations of T and P while keeping τα(T,P) constant. These properties observed in MMT offer experimental evidence of the dynamic correlation between α- and β-relaxations in pure small-molecule glass-formers.

Increasing the output power of the microwave is one of the most important development directions for high-power microwave (HPM) technology. However, when the output power is increased, the radio frequency breakdown would occur owing to superhigh electric field strength. This problem limits the power handling capability of a single-HPM generator, and this problem becomes more serious for high-frequency bands and long pulse. One solution to overcome this problem is coherent power combining, and coherent power combining can achieve an equivalent power of the order of mymargin TW. The relativistic klystron amplifier (RKA) is a promising candidate for coherent power combing owing to its character of controllable frequency and steady phase. However, the radiation power of RKA quickly decreases when the source is scaled up to higher frequencies such as ${X}$ -band, and moreover, the multigigawatts long pulse radiation from RKA at the ${X}$ -band has not yet been obtained experimentally. In this paper, we present investigations into an ${X}$ -band coaxial multibeam RKA, The power handling capability was increased by introducing 20 electron drift tubes and a four gaps extended interaction output cavity. The amplitude uniformity of the multiple electron beams was improved by optimized the anode and cathode configuration. Then, a radiation power of 2.2 GW with pulsewidth of 120 ns is generated experimentally; the working frequency and amplifier gain are 9.4GHz and 50 dB, respectively.

Relatively high abundance of 17α (H)-diahopane has been detected in source rock extracts in the Yabulai Basin, a lacustrine basin in northwest China. Gas chromatography-mass spectrometry (GC-MS), X-ray diffraction (XRD) and Field emission environment scanning electron microscope imaging (FE-ESEM) were used in combination with conventional geochemical parameters to unravel the enrichment mechanisms. Significant variations of 17α (H)-diahopane concentrations detected in the Xinhe Formation with similar maturity inferred that thermal evolution is not the unique factor inducing the compound generating. The sedimentation of samples rich in 17α (H)-diahopane usually occur under suboxic conditions. Results of mineralogy analysis suggested that samples with high content of 17α (H)-diahopane are rich in carbonate minerals (about 20 wt %), which might deposit in brackish-saline water depositional environment. Relatively high content of gammacerane is also consistent with the experimental results of XRD. Based on the viewpoint of Moldowan et al. (1991), the regular hopanes may be the precursor of the rearranged hopanes, with the Wagner-Meerwein rearrangement as the mechanism. In this reaction, the critical factor of methyl migration is the production of carbocation starting with dehydroxylation. We suggested a general scheme for the generation of 17α (H)-diahopane in this study. In lacustrine sediments, suboxic and brackish environment could catalyze the methyl migration accompanied by carbonate deposit. Its geochemical implication can be used to reconstruct lacustrine paleoenvironment and contribute to a better understanding on oil-oil correlation, oil-source rock correlation and petroleum system study.

Through relatively subtle changes in reaction conditions, we have been able to isolate four distinct Rh/Sn cluster compounds, [Rh@Sn10]3−, [Rh@Sn12]3−, [Rh2@Sn17]6− and [Rh3@Sn24]5–, from the reaction of K4Sn9 with [(COE)2Rh(μ-Cl)]2(COE = cyclooctene). The last of these has a hitherto unknown molecular topology, an edge-fused polyhedron containing three Rh@Sn10 subunits, and represents the largest endohedral Group 14 Zintl cluster yet to have been isolated from solution. DFT has been used to place these new species in the context of known cluster chemistry. ESI-MS experiments on the reaction mixtures reveal the ubiquitous presence of {RhSn8} fragments that may play a role in cluster growth.

Cuticular hydrocarbons form a barrier that protects terrestrial insects from water loss via the epicuticle. Lipophorin loads and transports lipids, including hydrocarbons, from one tissue to another. In some insects, the lipophorin receptor (LpR), which binds to lipophorin and accepts its lipid cargo, is essential for female fecundity because it mediates the incorporation of lipophorin by developing oocytes. However, it is unclear whether LpR is involved in the accumulation of cuticular hydrocarbons and its precise role in aphid reproduction remains unknown. We herein present the results of our molecular characterization, phylogenetic analysis, and functional annotation of the pea aphid (Acyrthosiphon pisum) LpR gene (ApLpR). This gene was transcribed throughout the A. pisum life cycle, but especially during the embryonic stage and in the abdominal cuticle. Furthermore, we optimized the RHA interference (RNAi) parameters by determining the ideal dose and duration for gene silencing in the pea aphid. We observed that the RNAi-based ApLpR suppression significantly decreased the internal and cuticular hydrocarbon contents as well as adult fecundity. Additionally, a deficiency in cuticular hydrocarbons increased the susceptibility of aphids to desiccation stress, with decreased survival rates under simulated drought conditions. Moreover, ApLpR expression levels significantly increased in response to the desiccation treatment. These results confirm that ApLpR is involved in transporting hydrocarbons and protecting aphids from desiccation stress. Furthermore, this gene is vital for aphid reproduction. Therefore, the ApLpR gene of A. pisum may be a novel RNAi target relevant for insect pest management.

The HotDisk thermal constants analyzer based on the transient plane source (TPS) technique can be used to measure the hydrate thermal conductivity. In order to improve the measurement accuracy, the HotDisk setting parameters, the sample preparation and measurement method are investigated in this paper. Firstly, the evaluation criteria are proposed to determine the optimal setting parameters, mainly the output power and measurement time. Four kinds of method of the sample preparation and thermal conductivity measurement in situ are proposed and discussed. The used samples include pure Tetrahydrofuran (THF) hydrate, ice and THF hydrate or ice bearing silica sand. The results show that the optimal parameters of the output power and measurement time depend on the sample. A high purity of sample can be obtained using the temperature oscillation-aging method and the accuracy of measurement can be further improved using the “increasing temperature-decreasing temperature” method.

All-inorganic CsPbX3 (X = I, Br, Cl) perovskite quantum dots (QDs) are emerging as potential candidates for photoelectric devices such as light-emitting diodes (LEDs), solar cells etc. due to their outstanding optical properties including tunable bandgap, narrow size distribution and high photoluminescence (PL) quantum yield (QY). However, instability originated from the strong anion-exchange effect and the lower melting temperature hinders their further practical application. Here, blue emission CsPbBr1.5Cl1.5 QDs with peak wavelength ∼450 nm are prepared by means of hot injection method, and mesoporous silica particles are introduced to wrap them. On one hand, the silica coat, protecting the core QDs from oxygen and humidity somewhat, the stability of the PL QYs and the luminescence of the CsPbBr1.5Cl1.5 QDs, as well as the emission and vision properties of the devices based on these QDs are improved evidently. On the other hand, by integrating the prepared blue emission CsPbBr1.5Cl1.5 QDs or the silica-coated CsPbBr1.5Cl1.5 QDs as single downconverters on violet chips with emission wavelength 365 nm, surprisingly, we observe a new peak ∼550 nm in the PL spectrum of the resultant devices, except for the originate blue emission. We speculate that the new emission peak, which is helpful for the construction of white LEDs (WLEDs), is originated from the bromide-enriched majority domains resulted from the photo-induced segregation of CsPbBr1.5Cl1.5 QDs. The fabricated WLEDs based on CsPbBr1.5Cl1.5@SiO2 QDs, in comparison with that based on CsPbBr1.5Cl1.5 QDs, exhibits stable color rendering index (CRI) with the least variation of 1.4, and stable color correlated temperature (CCT) with the least variation of 325 K. These results suggest that the large full width of half maximum of the new emission benefits for the construction of WLEDs, and mesoporous silica particles serving as coat layer hold great promise for the improvement of performance stability for the devices based on CsPbBr1.5Cl1.5@SiO2 QDs.

Development of new heterogeneous base catalysts for Knoevenagel condensation reactions is critical for practical applications. Herein, we demonstrate that carbon doped hexagonal boron nitride (BCN) exhibits a high catalytic activity for Knoevenagel condensation of benzaldehyde with malononitrile, producing benzylidene malononitrile under mild reaction conditions. An 81.9% conversion can be achieved over BCN after 15 min reaction time, which is 1.8 times with respect to hexagonal boron nitride (h-BN) and 27 times over C3N4. Moreover, the BCN catalyst could be easily separated and recycled for several runs without obvious deactivation. Experimental results, spectroscopic characterizations, combined with first-principle calculations, suggest the reaction likely follows a dissociative adsorption mechanism on the oxygen terminated BCN edge. The C atoms doping plays a vital role in promoting the desorption of the intermediates. This study can open up a new avenue for the Knoevenagel condensation reaction with metal-free catalysis.

The recent discovery of gravitational-wave burst GW150914 marks the coming of a new era of gravitational-wave astronomy, which provides a new window to study the physics of strong gravitational field, extremely massive stars, extremely high energy processes, and extremely early universe. In this article, we introduce the basic characters of gravitational waves in the Einstein's general relativity, their observational effects and main generation mechanisms, including the rotation of neutron stars, evolution of binary systems, and spontaneous generation in the inflation universe. Different sources produce the gravitational waves at quite different frequencies, which can be detected by different methods. In the lowest frequency range (f

Quantum dot-sensitized solar cells (QDSCs) are promising for future renewable sources. By addressing the issues on liquid-electrolyte leakage and sluggish charge transportation, a class of graphene oxide tailored polyacrylamide (PAAm/GO) gel electrolytes are synthesized for quasi-solid-state QDSC applications. The conducting pathways with interconnected GO species can catalyze reduction reaction from Sn2− to S2− and therefore shorten charge-transfer length. Upon illumination by simulated sunlight (AM1.5, 100 mW cm−2), the optimized QDSC with PAAm/0.9% GO yields a maximized power conversion efficiency of 4.10% in comparison with 1.78% for the device free of GO. Arising from the good retention of liquid electrolyte by three-dimensional PAAM/GO framework, the final quasi-solid-state QDSCs present good long-term stability.

A crucial issue faced by quantum dot solar cells (QDSC) is how to achieve a quantum dot material with high photoluminescence (PL) quantum yield and long excited state lifetime at the same time to maximize charge carrier collection efficiency. Here, we present a new type of Zn0.9Cd0.1S/ZnSe hetero-nanocrystals that have a staggered band alignment, i.e., a type-II structure by which the wave function overlap between electrons and holes is reduced, thereby leading to a significant enhancement in the PL lifetime. The resultant QD also exhibits a QY up to 75.4%, which is, to the best of our knowledge, the highest one for a type-II QD to date. In particular, we explore the underlying relationship between the broad tunability and energy level alignment of these hetero-nanocrystals, and we highlight the properties that have delivered QDSCs and light-emitting diodes.

In-situ grown nanoporous Zn-Cu catalysts were prepared by simply annealing a commercial brass foil at 500 °C in air, followed by electrochemical reduction. During the annealing process, Zn preferentially melted and migrated out of the framework of the alloy to form a thin layer of ZnO on its surface. Subsequent electroreduction created nanoporous Zn-enriched surface. The Zn concentration increased from 36% to 50% by 10 min, to 81% by 3 h, and to 87% by 12 h annealing treatment while the average pore size decreased from 290 nm to 120 nm as the annealing time increased from 1 h to 12 h. Faradaic efficiency of CO2 reduction to CO and HCOOH was enhanced by nearly 4 and 6 times, respectively, as compared to untreated brass foils. The nanoporous Zn-Cu catalyst presented a stable ratio of CO/H2 and a steady working current density in a continuous electrolysis of 18 h in 0.5 M KHCO3 solution.

An anaerobic ammonium oxidation (anammox) membrane bioreactor operated at 25 °C was used to investigate nitrogen removal under different operation conditions, namely, different sludge retention time (SRT) and nitrogen loading rate (NLR). The inhibition processes caused by high substance concentrations and over-loading were able to be circumvented by various adjustment methods. Furthermore, specific anammox activity (SAA) tests were performed to evaluate the effects of ammonium and nitrite on the anammox sludge. Over an SRT of 500 d, the content of volatile suspended solids (VSS) gradually increased from 125 mg/L to 5590 mg/L, and the maximum nitrogen removal rate (NRR) reached 1.18 kg N/m3/d. When the SRT was decreased to 50 d, the sludge concentration declined gradually, which necessitated an increase in the sludge loading rate (SLR), and the maximum sludge nitrogen removal rate (SNRR) of 0.67 g total nitrogen (TN)/g VSS/d was achieved at this time.

Copper has been intensively investigated as an electrocatalyst for electrochemical reduction of aqueous nitrate. Here we report preparation of Cu electrocatalyst by electrochemical deposition of Cu...

Bifacial solar cells that can generate electricity from either front or rear side are regarded as advanced photovoltaics for markedly increased photoelectric conversion efficiency. We present here the fabrication of transparent RuSe counter electrodes by an alternating electrodeposition method for bifacial dye-sensitized solar cells (DSSCs). The catalytic and photovoltaics performances are maximized by tuning stoichiometric Ru/Se ratio and bilayer number. Upon irradiation by AM1.5 (100 mW cm−2), the device yields a maximized front efficiency of 8.72% and a rear efficiency of 5.9%, arising from the >80%-transparency of RuSe electrode in visible light region. This strategy provides new opportunities for fabricating high-performance DSSCs.