Search

Effective carbon source plays a key role in denitrification process in membrane bioreactors (MBRs). In this study, alkali-rice straw was applied to a submerged hybrid MBR to achieve the nitrogen removal enhancement. It was found that total nitrogen (TN) removal of MBR with 1.4 g/d alkali-rice straw addition was 60.8% ± 1.5%, much higher than 44.5% ± 2.3%, 28.9% ± 5.4% from the MBR with 1.4 g/d normal rice straw addition and with 3.0 g/L PVC carrier addition, respectively, but lower than 77.5% ± 3.8% from the MBR with 4.0 g/d ethanol addition. However, chemical oxygen demand (COD) removal of MBR with 1.4 g/d alkali-rice straw addition was 94.6% ± 0.2% higher than 93.2% ± 0.3%, 91.8% ± 0.2% and 90.0% ± 0.4% from the MBR with 1.4 g/d rice straw addition, with 3.0 g/L PVC carrier addition, and with 4.0 g/d ethanol addition, respectively. Though the effect of alkali-rice straw on carbon release was not comparable with ethanol, it could have longer carbon releasing period to improve the carbon utilization rate, provide space for bacterial attachment, and promote the granular biofilm formation to reduce biofouling and increase COD removal efficiency. With alkali-rice straw addition, the dominant microbial community (Curvibacter, Nitrosomonas, Pseudomonas, Magnetospirillum, Paracoccus) in membrane bioreactor (MBR) was different from that with addition of other carbon source. Among these bacteria, the denitrifiers were dominantly expressed by nirS gene, and quantitative polymerase chain reaction of nirS gene in MBR with alkali-rice straw addition showed that its abundance was greatly higher than that with common rice straw addition. In summary, alkali-rice straw could serve as effective carbon source to enhance TN removals in MBRs. [ABSTRACT FROM AUTHOR]

Interior bearingless permanent magnet synchronous motors (IBPMSMs) are a new type of machines having two sets of windings in the stator, offering no lubrication and no mechanical friction, high efficiency, robust rotor construction, hybrid torque production nature and flux-weakening capability. In this paper, the suspension force modeling and the static electromagnetic characteristics of an IBPMSM are studied. The suspension force model of the IBPMSM is established and investigated based on the Maxwell tensor method. And then the static electromagnetic characteristics, including permanent magnet (PM) flux linkage, EMF, inductances, electromagnetic torque and suspension force, are discussed with the finite element analysis (FEA) method. The electromagnetic characteristics of the IBPMSM are very helpful for the design and optimization of the motor. The effectiveness of the proposed suspension force mathematical model is verified by comparing the theoretical results with FEA-based predictions. The work in this paper lays an important foundation for the optimization design and control strategies of the IBPMSM. [ABSTRACT FROM AUTHOR]

We demonstrate the generation of 92 nm (–3 dB bandwidth) flat-topped ultrabroad stimulation emission from a chirped InAs/InP quantum dot (QD) laser. A greatly enhanced bandwidth of the gain spectrum is achieved, which is attributed to the additionally broadened quantum dot energy levels utilizing gradually changed height of QDs in the stacked active layers. The laser exhibits a maximum output power of 0.35W under pulsed conditions, and the average spectral power density of above 3.8 mW/nm is obtained. The ultrabroad lasing spectrum in the wavelength interval of 1.49–1.61 µm covering S-C-L bands makes such a laser potentially useful as an optical source for various applications being compatible with silica fibers. [ABSTRACT FROM AUTHOR]

Recent studies reported that brassinosteroids (BRs) can induce plant tolerance to different environmental stresses via the nitric oxide (NO) signaling pathway. Previous reports have indicated that alternative oxidase (AOX) plays an important role in plants under various stresses. The mechanisms governing how NO is involved as a signal molecule which connects BR with AOX in regulating stress tolerance are still unknown. Recently, we found that Nicotiana benthamiana seedlings which were pretreated with BR have more tolerance to salt stress, accompanied with an increase of CN-resistant respiration. Our results suggested that pretreatment with 0.1 μM brassinolide (BL, the most active brassinosteroid) alleviated salt-induced oxidative damage and increased the NbAOX1 transcript level. Application of 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidazoline-1-1-oxyl-3-oxide (cPTIO, an NO scavenger) or virus-induced gene silencing of nitrate reductase (NR) and nitric oxide synthase (NOS)-like enzyme compromised the BRs-induced alternative respiratory pathway. Furthermore, pretreatment with specific chemical inhibitors of NR and NOS or gene silencing experiments decreased plant resistance to salt stress which also compromised BRs-induced salt stress tolerance. In conclusion, NO is involved in BRs-induced AOX capability which plays essential roles in salt tolerance in N. benthamiana seedlings. [ABSTRACT FROM AUTHOR]

Large signal modulation characteristics of the simultaneous ground-state (GS) and excited-state (ES) lasing quantum dot lasers are theoretically investigated. Relaxation oscillations of '0 → 1' and '1 → 0' in the GS lasing region (Region I), the transition region from GS lasing to two-state lasing (Region II) and the two-state lasing region (Region III) are compared and analyzed. It is found that the overshooting power and settling time in both Regions I and III decrease as the bias current increases. However, there exist abnormal behaviors of the overshooting power and settling time in Region II owing to the occurrence of ES lasing, which lead to fuzzy eye diagrams of the GS and ES lasing. Moreover, the ES lasing in Region III possesses much better eye diagrams because of its shorter settling time and smaller overshooting power over the GS lasing in Region I. [ABSTRACT FROM AUTHOR]

The grain microstructure of molten pool during the solidification of TC4 titanium alloy in the single point laser cladding was investigated based on the CAFE model which is the cellular automaton (CA) coupled with the finite element (FE) method. The correct temperature field is the prerequisite for simulating the grain microstructure during the solidification of the molten pool. The model solves the energy equation by the FE method to simulate the temperature distribution in the molten pool of the single point laser cladding. Based on the temperature field, the solidification microstructure of the molten pool is also simulated with the CAFE method. The results show that the maximum temperature in the molten pool increases with the laser power and the scanning rate. The laser power has a larger influence on the temperature distribution of the molten pool than the scanning rate. During the solidification of the molten pool, the heat at the bottom of the molten pool transfers faster than that at the top of the molten pool. The grains rapidly grow into the molten pool, and then the columnar crystals are formed. This study has a very important significance for improving the quality of the structure parts manufactured through the laser cladding forming. [ABSTRACT FROM AUTHOR]

The optical performance of a grating-coupled external cavity laser based on InAs/InP quantum dots is investigated. Continuous tuning from 1391 nm to 1468 nm is realized at an injection current of 1900 mA. With the injection current increasing to 2300 mA, the tuning is blue shifted to some extent to the range from 1383 nm to 1461 nm. By combining the effect of the injection current with the grating tuning, the total tuning bandwidth of the external cavity quantum-dot laser can reach up to 85 nm. The dependence of the threshold current on the tuning wavelength is also presented. [ABSTRACT FROM AUTHOR]

Metalorganic chemical vapor deposition growth of InAs/GaSb superlattices is reported using an AsxSb1-x plane that connects the InAs and GaSb layers to compensate the tensile strain introduced by the InAs layers. The effects of gas switching sequences for growing the AsxSb1-x planes on the interface structure and crystalline quality of InAs/GaSb superlattices were investigated by Raman scattering spectroscopy and X-ray diffraction. It is found that uniform interfaces and high-quality superlattice can be obtained by growing the AsxSb1-x planes through the exchange interaction of As and Sb atoms at the surfaces of InAs or GaSb layers. [ABSTRACT FROM AUTHOR]

We report on photoluminescence (PL) emission with long wavelength for quantum structure by the sub-monolayer (SML) growth technique on GaAs (001) substrate. It is found that the PL emission wavelength can be controlled by controlling the SML InAs deposition amount. At 12 K, the PL peak position of the grown samples changes from about 1.66 to 1.78 μm. At 120 K, the PL emission of a sample reaches 1.91 μm. The physical mechanism responsible for the measured long wavelength PL emission may be related to strong In segregation and intermixing effects occurred in the structure grown by SML growth technique. [ABSTRACT FROM AUTHOR]

The object detection of remote sensing image often has low accuracy and high missed or false detection rate due to the large number of small objects, instance level noise and cloud occlusion. In this paper, a new object detection model based on SRGAN and YOLOV3 is proposed, which is called SR-YOLO. It solves the problems of SRGAN network sensitivity to hyper-parameters and modal collapse. Meanwhile, The FPN network in YOLOv3 is replaced by PANet, shortened the distance between the lowest and the highest layers, and the SR-YOLO model has strong robustness and high detection ability by using the enhanced path to enrich the characteristics of each layer. The experimental results on the UCAS-High Resolution Aerial Object Detection Dataset showed SR-YOLO has achieved excellent performance. Compared with YOLOv3, the average precision (AP) of SR-YOLO increased from 92.35% to 96.13%, the log-average miss rate (MR-2) decreased from 22% to 14%, and the Recall rate increased from 91.36% to 95.12%. [ABSTRACT FROM AUTHOR]

Large-signal modulation capability, as an important performance indicator, is directly related to the high-speed optical communication technology involved. We experimentally and theoretically investigate the large-signal modulation characteristics of the simultaneous ground-state (GS) and the excited-state (ES) lasing in InAs/GaAs quantum dot laser diodes. The large-signal modulation capability of total light intensity in the transition regime from GS lasing to two-state lasing is unchanged as the bias-current increases. However, GS and ES large-signal eye diagrams show obvious variations during the transition. Relaxation oscillations and large-signal eye diagrams for GS, ES, and total light intensities are numerically simulated and analyzed in detail by using a rate-equation model. The findings show that a complementary relationship between the light intensities for GS and ES lasing exists in both the transition regime and the two-state lasing regime, leading to a much smaller overshooting power and a shorter settling time for the total light intensity. Therefore, the eye diagrams of GS or ES lasing are diffuse whereas those of total light intensity are constant as the bias-current increases in the transition regime. [ABSTRACT FROM AUTHOR]

We report the growth of InAs/GaSb core–shell heterostructure nanowires with smooth sidewalls on Si substrates using metal–organic chemical vapor deposition with no assistance from foreign catalysts. Sb adatoms were observed to strongly influence the morphology of the GaSb shell. In particular, Ga droplets form on the nanowire tips when a relatively low TMSb flow rate is used, whereas the droplets are missing and the radial growth of the GaSb is enhanced due to a reduction in the diffusion length of the Ga adatoms when the TMSb flow rate is increased. Moreover, transmission electron microscopy measurements revealed that the GaSb shell coherently grew on the InAs core. The results obtained here show that the InAs/GaSb core–shell nanowires grown using the Si platform have strong potential in the fabrication of future nanometer-scale devices and in the study of fundamental quantum physics. [ABSTRACT FROM AUTHOR]

Aiming at the problem of how to give full play to the reverse extrusion ability of bolt to the surrounding rock to make the interface stress balance quickly and enhance the active support effect, we propose the anchorage method of radial pressurization. By adding expansion agent into cement grout to form self-stress slurry, radial expansion stress is generated on the pore wall under the constraint of rock mass, and the stress state of surrounding rock is improved. Under the constraint of thin-walled steel pipe, the radial expansion stress generated by the cement slurry stone body mixed with different amounts of expansion agent is used as a different pressurization variable, and the expansion stress of steel tube wall was measured by static strain gauge and the deformation law of radial stress in stone body with different expansion agent content was analyzed. The finite element software ABAQUS is used to simulate the deformation characteristics of the surrounding rock under different pressurization variables, and the stress field and displacement field of the surrounding rock under stress and deformation are systematically studied. The results show that the radial stress and strength of cement slurry stone with 7% expansion agent are better than those of other proportions, and the compressive stress between cement slurry stone and pore wall increases obviously, resulting in expansion effect. With the increase of radial stress of grout stone body, the compressive stress increases by 65% and the deformation increases by 71% on average, and the radial stress of surrounding rock decreases with the increase of distance from drilling hole.

In order to explore the impact of antibiotics (enrofloxacin) on microbial community in aquatic environment, an indoor aquatic ecological model was built, and different concentrations of enrofloxacin (0.05, 0.5, 5, and 50 mg/L) were added in the aquatic ecological model. In addition, the water and sediment samples were collected on the 0, 7, 30, and 60 days, and the changes in microbial community were studied through 16S rDNA high-throughput sequencing. The results showed that when the concentration of enrofloxacin was 50 mg/L, the relative abundance of Actinomycetes was increased. In the water, the bacterial richness and diversity communities first decreased and then gradually recovered with the passage of time; On the 7th day, the diversity and richness index of species in the treatment groups with enrofloxacin at 5 and 50 mg/L decreased to the lowest; On the 30th day, the diversity and richness index of species began to rise; On the 60th day, the diversity index and richness index of water species began to increase, while the diversity index and richness index of sediment species decreased. In conclusion, the addition of enrofloxacin negatively affected the microbial community structure in an indoor aquatic ecological model, 50 mg/L enrofloxacin could increase the relative abundance of Actinomycetes, and decrease the diversity and richness index of water and sediment.

Despite numerous studies on transcriptional level regulation by single genes in drug producing Actinomyces, the global regulation based on epigenetic modification is not well explored. N4-methylcytosine (m4C), an abundant epigenetic marker in Actinomycetes’ genome, but its regulatory mechanism remains unclear. In this study, we identify a m4C methyltransferase (SroLm3) in Streptomyces roseosporus L30 and multi-omics studies were performed and revealed SroLm3 as a global regulator of secondary metabolism. Notably, three BGCs in ΔsroLm3 strain exhibited decreased expression compared to wild type. In-frame deletion of sroLm3 in S.roseosporus L30 further revealed its role in enhancing daptomycin production. In summary, we characterized a m4C methyltransferase, revealed the function of m4C in secondary metabolism regulation and biosynthesis of red pigment, and mapped a series of novel regulators for daptomycin biosynthesis dominated by m4C methylation. Our research further indicated that m4C DNA methylation may contribute to a metabolic switch from primary to secondary metabolism in Actinomyces. [ABSTRACT FROM AUTHOR]

As the intermittency and uncertainty of photovoltaic (PV) power generation poses considerable challenges to the power system operation, accurate PV generation estimates are critical for the distribution operation, maintenance, and demand response program implementation because of the increasing usage of distributed PVs. Currently, most residential PVs are installed behind the meter, with only the net load available to the utilities. Therefore, a method for disaggregating the residential PV generation from the net load data is needed to enhance the grid-edge observability. In this study, an unsupervised PV capacity estimation method based on net metering data is proposed, for estimating the PV capacity in the customer's premise based on the distribution characteristics of nocturnal and diurnal net load extremes. Then, the PV generation disaggregation method is presented. Based on the analysis of the correlation between the nocturnal and diurnal actual loads and the correlation between the PV capacity and their actual PV generation, the PV generation of customers is estimated by applying linear fitting of multiple typical solar exemplars and then disaggregating them into hourly-resolution power profiles. Finally, the anomalies of disaggregated PV power are calibrated and corrected using the estimated capacity. Experiment results on a real-world hourly dataset involving 260 customers show that the proposed PV capacity estimation method achieves good accuracy because of the advantages of robustness and low complexity. Compared with the state-of-the-art PV disaggregation algorithm, the proposed method exhibits a reduction of over 15% for the mean absolute percentage error and over 20% for the root mean square error. [ABSTRACT FROM AUTHOR]

In recent years, as the third-generation of drugs, new psychoactive substances （NPS） have expanded rapidly and become a serious concern for China’s anti-drug prevention and control system. As a new drug monitoring technology in the current anti-drug field, wastewater analysis is an objective, real-time, accurate, convenient and effective drug monitoring method. In recent years, it has gradually been applied to the monitoring of NPS. This study summarizes wastewater sample collection, target stability research, wastewater sample pretreatment, wastewater sample analysis methods, target NPS consumption calculations and actual monitoring applications, with a view to the construction of a monitoring system for NPS in wastewater, real-time and accurate grasp of information on the use of NPS in cities, the reflection of the actual consumption of different types of NPS and consumption trends in a short period of time, and prediction of the development trend of abused use, which is of great significance for combating NPS crimes, serving and guaranteeing the personal safety of the people, and maintaining social stability.

Graphical abstract Highlights • Different preservation methods of nanoscale zero-valent iron were proposed. • Simplified the prepare procedure of nanoscale zero-valent iron apparently. • The undried nanoscale zero-valent iron has high adsorption capacity and adsorption rate for Pb(II). • Effects of dosage, pH, initial lead concentration and reaction time were studied. Abstract In this study, different nanoscale zero-valent irons (nZVI) were prepared in order to improve their stability and reactivity to heavy metal lead (Pb (II)). The composition, particle size and morphology of obtained nZVI were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscope (SEM). The effects of nZVI dosage, pH, initial Pb (II) concentration and reaction time on the removal efficacy of Pb (II) were investigated. The results show that undried nZVI has more active sites due to its weaker oxidation, and thus the removal efficiency of Pb(II) by undried nZVI was higher than that by dried nZVI. As a result, the same removal efficiency could be achieved with the use of less undried nZVI for the identical concentration of Pb(II). Furthermore, the experimental procedure could be apparently simplified, which eliminates the steps of washing, separation and dehydration compared with the traditional preparation method. The experimental data could be well fitted by the Langmuir adsorption isotherm model, and the maximum adsorption capacity of dried and undried nZVI is 671.14 and 807.23 mg·g−1 at pH 6, respectively. The experimental data followed the pseudo second-order kinetic model with a kinetic constant of 7.65 × 10−4 and 1.39 × 10−3 for undried and dried nZVI, respectively. In conclusion, undried nZVI had high adsorption capacity and adsorption rate for Pb(II) in the solution. [ABSTRACT FROM AUTHOR]

Daptomycin is a potent cyclic lipopeptide antibiotic. It is widely used against various Gram-positive bacterial pathogens. Historically, a poor understanding of the transcriptional regulation of daptomycin biosynthesis has limited the options for targeted genetic engineering toward titer improvement. Here, we isolated a TetR family transcriptional regulator, DepR1, from the industrial producer Streptomyces roseosporus SW0702 using a biotinylated dptE promoter (dptEp) as a probe. The direct interaction between DepR1 and dptEp then was confirmed by electrophoretic mobility shift assays and DNase I footprinting assays. The deletion of depR1 led to a reduction in dptEp activity and the cessation of daptomycin production. The iidepR1 mutant produced less red pigment and failed to sporulate on R5 medium. This suggests that DepR1 plays a positive role in the control of morphological differentiation. Moreover, DepR1 was positively autoregulated by directly binding to its own promoter. This might account for the positive feedback regulation of daptomycin production. Based on these positive effects, genetic engineering by overexpression of depR1 raised daptomycin production and shortened the fermentation period both in flask and in fermentor. [ABSTRACT FROM AUTHOR]

The three-dimensional flow physical model of any stage of the 20BZ4 multistage centrifugal pump is built which includes inlet region, impeller flow region, guide-vane flow region and exit region. The three-dimensional unsteady turbulent flow numerical model is created based on Navier-Stoke solver and standard K-ε turbulent equations. The method of multireference frame (MRF) and SIMPLE algorithmare used to simulate the flow inmultistage centrifugal pump based on FLUENT software. The distributions of relative velocity, absolute velocity, static pressure, and total pressure in guide vanes and impellers under design condition are analyzed. The simulation results show that the flow in impeller is mostly uniform, without eddy, backflow, and separation flow, and jet-wake phenomenon appears only along individual blades. There is secondary flow at blade end and exit of guide vane. Due to the different blade numbers of guide vane and impeller, the total pressure distribution is asymmetric. This paper also simulates the flow under different working conditions to predict the hydraulic performances of centrifugal pump and external characteristics including flow-lift, flow-shaft power, and flow-efficiency are attained. The simulation results are compared with the experimental results, and because of the mechanical losses and volume loss ignored, there is a little difference between them. [ABSTRACT FROM AUTHOR]

Objectives: Our recent report indicates that breviscapine play a protective role of the kidney by down-regulating transforming growth factor-β1(TGF-β1), α-smooth muscle actin (α-SMA) and alleviating interstitial fibrosis following unilateral ureteral obstruction (UUO). In this study, we investigate the effect of breviscapine on changes of renal water and sodium transport proteins in response to UUO., Materials and Methods: Male Sprague-Dawley rats were divided into 3 groups, sham group, UUO group and UUO treat with breviscapine. After 4, 7 and 14 days, histologic changes and interstitial collagen were determined microscopically following hematoxylin and eosin (H&E) and Masson's trichrome staining. The expression of Aquaporins (AQP-2) and γ-epithelial sodium channel (γ-ENaC) were investigated using immunohistochemistry and Western blot in each group., Results: Breviscapine treatment decrease the tubular injury index and the degree of interstitial collagen deposition significantly compared with the UUO group (P<0.05). Breviscapine treatment also significantly reduced downregulation of AQP2 and γ-ENaC compared to those subjected to the same time course of obstruction in UUO group (P<0.05)., Conclusion: These results demonstrate that breviscapine could prevent downregulation of renal water and sodium transport proteins in response to UUO so as to protect obstructed kidney.