Dual-Schottky-junctions coupling device based on ultra-longβ-Ga_(2)O_(3)single-crystal nanobelt and its photoelectric properties

High qualityβ-Ga_(2)O_(3)single crystal nanobelts with length of 2−3 mm and width from tens of microns to 132μm were synthesized by carbothermal reduction method.Based on the grown nanobelt with the length of 600μm,the dual-Schottky-junctions coupling device(DSCD)was fabricated.Due to the electrically floating Ga_(2)O_(3)nanobelt region coupling with the double Schottky-junctions,the current I_(S2)increases firstly and rapidly reaches into saturation as increase the voltage V_(S2).The saturation current is about 10 pA,which is two orders of magnitude lower than that of a single Schottky-junction.In the case of solar-blind ultraviolet(UV)light irradiation,the photogenerated electrons further aggravate the coupling physical mechanism in device.I_(S2)increases as the intensity of UV light increases.Under the UV light of 1820μW/cm^(2),I_(S2)quickly enters the saturation state.At V_(S2)=10 V,photo-to-dark current ratio(PDCR)of the device reaches more than 104,the external quantum efficiency(EQE)is 1.6×10^(3)%,and the detectivity(D*)is 7.5×10^(12)Jones.In addition,the device has a very short rise and decay times of 25−54 ms under different positive and negative bias.DSCD shows unique electrical and optical control characteristics,which will open a new way for the application of nanobelt-based devices.

Preparation of Sn-doped Ga_(2)O_(3) thin films and their solar-blind photoelectric detection performance

Sn doping is an effective way to improve the response rate of Ga_(2)O_(3) film based solar-blind detectors. In this paper,Sn-doped Ga_(2)O_(3) films were prepared on a sapphire substrate by radio frequency magnetron sputtering. The films were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and ultraviolet visible spectroscopy, and the effect of annealing atmosphere on the properties of films was studied. The Ga_(2)O_(3) films changed from amorphous to β-Ga_(2)O_(3) after annealing at 900 °C. The films were composed of micro crystalline particles with a diameter of about 5–20 nm.The β-Ga_(2)O_(3) had high transmittance for wavelengths above 300 nm, and obvious absorption for solar-blind signals at 200–280 nm.The metal semiconductor metal type solar-blind detectors were prepared. The detector based on Sn-doped β-Ga_(2)O_(3) thin film annealed in N_2 has the best response performance to 254 nm light. The photo-current is 10 μA at 20 V, the dark-current is 5.76 pA,the photo dark current ratio is 1.7 × 10~6, the response rate is 12.47 A/W, the external quantum efficiency is 6.09 × 10~3%, the specific detection rate is 2.61 × 10~(12) Jones, the response time and recovery time are 378 and 90 ms, respectively.

Synthesis of Fe^(3+)-doped Aminated Lignin as A Peroxidase Mimic for Colorimetric Detection of H_(2)O_(2) and Glucose

Peroxidase plays an important role in living systems;however,its storage difficulty and easy inactivation have limited its applications in complex environments.To address these problems,herein,we proposed a method to synthesize peroxidase mimics by amination,carbonization,and Fe^(3+)-doping of industrial alkali lignin.The Fe^(3+)-doped lignin-based peroxidase mimic(Fe-LPM),with active centers of coordination between Fe^(3+)and N atoms,showed higher tolerance to pH value and temperature than natural peroxidase.Using Fe-LPM,10-100 mmol/L of H_(2)O_(2) and glucose could be colorimetrically detected with the lowest detection limits of 80μmol/L and 1.5 mmol/L and visual detection limits of 1.0 mmol/L and 10 mmol/L,respectively.The Fe-LPM maintained peroxidase-like activity after 10 cycles and could even be used for H_(2)O_(2) detection in practical samples.This work not only provides a new approach to synthesize peroxidase mimics using biomass materials but also promotes the high-value utilization of lignin.

Substitution of His260 residue alters the thermostability of Pseudoalteromonas carrageenovora arylsulfatase

This study aimed to improve the thermostability of arylsulfatase from Pseudoalteromonas carrageenovora. A library of P. carrageenovora arylsulfatase mutants was constructed by introducing random mutagenesis using error-prone PCR. After screening, two mutants of H260L and D84A/H260L showed enhanced thermal stability than the wild-type predecessor (WT). Site-directed mutagenesis demonstrated that only amino acid residue at Position 260 plays an important role in the thermostability of P. carrageenovora arylsulfatase. Thermal inactivation analysis showed that the half-life (t1/2) values at 55°C for H260L, H260I, H260Q, H260F and H260R were 40.6, 48.4, 30.9, 29.1 and 34.5 min, respectively, while that of WT was 9.1 min. Structure modeling demonstrated that the additional hydrogen bonds and/or optimization of surface charge-charge interactions could be responsible for the increased thermostability imparted by H260L, H260I, H260Q, H260F and H260R.

苯乙烯-间戊二烯-对甲基苯乙烯阴离子共聚合

间戊二烯单体与苯乙烯可以通过阴离子共聚合实现特殊交替序列结构共聚物,此类材料在高抗冲击性树脂和增韧材料方面有特殊用途。本文利用苯乙烯(ST)、间戊二烯(PD)和对甲基苯乙烯(MST)的阴离子共聚合方法,通过“一步法”制备了新型序列共聚物,并对聚合动力学及共聚物微观序列结构进行了系统研究。研究表明:均聚单体活性ST>MST>>PD,聚合反应动力学级数n=1,单体均可以定量转化;^(1)H-NMR在线分析表明,PD/ST和PD/MST共聚单体等摩尔消耗,结合竞聚率数据推测PD倾向与苯乙烯类单体均可形成交替结构,且PD主要是1,4-加成方式嵌入主链;三元共聚活性可控程度极佳,相对分子质量与转化率成良好的线性关系,分子量分布低于1.10;三元共聚物中间戊二烯组成(FPD=0.5)似乎与转化率无关,但ST和MST共聚单体含量均与转化率成线性关系;基于PD独特的二元交替共聚行为,推测了可能共聚合机理。

聚(对苯二甲酸丁二醇酯-co-对苯二甲酸丙二醇酯)基荧光共聚酯的制备及性能

以对苯二甲酸二甲酯、丁二醇、丙二醇、四氯苝-铜配位聚合物网络酐(TTAD)为单体,通过熔融缩聚反应制备了一系列荧光共聚酯,研究了TTAD含量对共聚酯荧光性能的影响。利用紫外分光光度计、核磁共振仪、荧光分光光度计等表征了共聚酯的化学结构和荧光量子效率。结果表明,共聚酯具有预期的化学结构,且具有高亮度、高荧光量子产率的特征,随着TTAD含量的增加,共聚酯呈现出从黄绿色到橙红色的荧光,不同共聚酯间的荧光差异明显,TTAD在共聚酯中不会发生聚集荧光猝灭。

Overexpression and characterization of a thermostable β-agarase producing neoagarotetraose from a marine isolate Microbulbifer sp.AG1

An agarase gene containing 1 302 bp was cloned from Microbulbifer sp. AG1. It encoded a mature protein of 413 amino acids plus a 20-residue signal peptide. The recombinant enzyme without the signal peptide was expressed and purified from Escherichia coli BL21(DE3). When agarose was used as a substrate, the optimal temperature and pH for the enzyme were 60℃ and 7.5, respectively. The recombinant agarase showed excellent thermostability with 67% and 19% of residual activities after incubation at 50℃ and 60℃ for 1 h, respectively.Except SDS, the recombinant agarase had a relatively good resistance against the detected inhibitors, detergents and urea denaturant. Thin layer chromatography analysis and enzyme assay using p-nitrophenyl-α/β-Dgalactopyranoside revealed that the recombinant agarase was a β-agarase that degraded agarose into neoagarotetraose as the main end product. The enzymatic hydrolysis products with different degree of polymerization exhibited the antioxidant activities.

Mechanical Properties and Microcosmic Properties of Self-Compacting Concrete Modified by Compound Admixtures

It has become a research hotspot to explore raw material substitutes of concrete.It is important to research the mechanical properties of self-compacting concrete(SCC)with slag powder(SP)and rubber particle(RP)replacing cement and coarse aggregate,respectively.12 kinds of composite modified self-compacting concrete(CMSCC)specimens were prepared by using 10%,20%and 30%SP and 30%,40%,50%and 60%RP.The rheological properties,mechanical properties and microstructure of the CMSCC were investigated.Results indicate that the workability,compressive strength,splitting tensile strength and flexural strength of CMSCC prepared by 20%SP and less than 40%RP are improved.In order to maximize the utilization of waste materials,20%SP and 40%RP can be used as the optimal ratio of the combined modifier.The microstructure shows that the addition of proper amount of SP is conducive to the formation of increasingly more uniform C-S-H gel.C-SH gel can fill the internal pores of the sample and enhance the adhesion between the aggregate,thus improving the mechanical properties of CMSCC.RP has a rougher surface and lower density and stiffness,which inhibits the workability and mechanical properties of CMSCC.The above research results have important theoretical and practical significance for the selection of raw materials of self-compacting concrete and the rational use of industrial wastes.

Multilayer graphene refractive index tuning by optical power

Graphene's optical absorption coefficient increases linearly with the number of layers making it more effective in the construction of optical tuning graphene-based devices. Refractive index(RI) is one of the important optical parameters of the graphene for accurately describing its optical characteristics and further applications. In view of the RI research of the multilayer graphene is lacking and existing measurement methods are complicated. Optical power tuning RI of multilayer graphene is investigated using a simple measurement and no temperature cross sensitivity all optical fiber sensing structure.Optical power tuning RI characteristics of multilayer graphene are studied by tuning the introducing broad band light power from 0.57 mW to 22.7 m W. Different thickness graphene coating shows different tuning efficiency. At 4.86-μm thickness,a 3.433-nm Bragg wavelength shift is obtained with 156.2-pm/mW wavelength versus optical power tuning sensitivity corresponding to 3.25×10~3 RI change and 0.154 URI/W(URI, unit of RI) RI optical power tuning efficiency.

Quantization of the band at the surface of charge density wave material 2H-TaSe_(2)

By using angle-resolvea photoemission spectroscopy(ARPES) combined with the first-principies electronic structure calculations,we report the quantized states at the surface of a single crystal 2 H-TaSe_(2).We have observed sub-bands of quantized states at the three-dimensional Brillouin zone center due to a highly dispersive band with light effective mass along k_(z) direction.The quantized sub-bands shift upward towards E_(F) while the bulk band at Γ shifts downward with the decrease of temperature across charge density wave(CDW) formation.The band shifts could be intimately related to the CDW.While neither the two-dimensional Fermi-surface nesting nor purely strong electron-phonon coupling can explain the mechanism of CDW in 2 H-TaSe_(2),our experiment may ignite the interest in understanding the CDW mechanism in this family.

Elastic Resource Allocation for Multi-Granularity Multicasting Traffic in OFDM-Based Optical Networks

With the increasing requirements of the multicast services in the whole data traffic service, the optical multicast technology becomes a key technology supporting wide bandwidth and high speed multicasting communication. The transmission efficiency, capacity and robustness of optical multicast network can be further improved by introducing network coding technology into optical multicast networks. Meanwhile, facing to demand of emerging rate-variable multi-granularity multicast service, a multi-path transmission scheme based on network coding for routing and spectrum allocation (RSA) is proposed. It can not only allocate spectrum resources effectively and flexibly for various-rate multicast traffic, but also balance the network load, improve network throughput and reduce transmission blocking rate. In this paper, RSA problem is decomposed into two subproblems, namely routing allocation based on network coding and spectrum allocation based on maximum spectrum first (MSF) strategy, which are solved sequentially. Simulation experiments are carried out to analyze transmission performance with proposed RSA scheme. The simulation results show that the proposed RSA mechanism can allocate spectrum resources efficiently and flexibly for multi-granularity multicast traffic. Compared with RSA schemes based on shortest path tree (SPT) and minimal spanning tree (MST), the proposed RSA scheme is more efficient for spectrum resource utilization and load balancing, and spectrum resource is saved more than 20%.

烧结钕铁硼材料压痕断裂力学机理研究

本文根据单金刚石磨粒磨削模型和高等弹塑性力学中的空间问题,把磨削加工的过程中的力分为法向分力和切向分力,建立钕铁硼材料单金刚石的磨粒磨削的理论模型。然后将其等效成单金刚石磨粒的压痕试验,观察到其压痕均为巴氏裂纹。最后,通过实验论证了钕铁硼材料磨削加工材料去除机理,对材料受载后其形貌变化和裂纹的形成及扩展过程进行了详细阐述。此次研究为钕铁硼材料磨削参数和加工方式的选择提供理论依据。

Growth and Optical Applications of Centimeter-Long ZnO Nanocombs

Ultralong ZnO nanocombs have been synthesized on silicon substrates with a high growth rate of~7μm/s using a simple“thermal evaporation and condensation”method promoted by Cu catalysts.The lengths of the ZnO nanocombs range from several millimeters to more than one centimeter and the diameters of the branches are about 300 nm.The growth mechanism of the ultralong nanocombs and the catalytic behavior of the copper are discussed.The nanocombs were readily separated and their applications as optical polarizer and grating were investigated.The results show that the ultralong ZnO nanocombs can act as effective optical components in miniaturized integrated optics systems.

L3 French Conceptual Transfer in the Acquisition of L2 English Motion Events among Native Chinese Speakers

The theory of conceptual transfer investigates the extent to which the perception of a previously learned language influences the conceptualization of a language learned subsequently.To provide further evidence supporting such hypotheses,the present study invites three groups of native Chinese-speaking college students to finish selected language tasks with an aim to explore whether the perception of L3 French motion verbs presents itself in the acquisition of L2 English path particles.All three participating groups have learned English as L2 and reached intermediate level,with one group being Chinese majors and the other two specializing in French with different proficiency levels.The findings suggest L3 would exhibit negative transfer in the acquisition of motion events in L2 English.Based on the analysis of participants’retrospective data and the comparison between Chinese group and French groups,the nature of such transfer is claimed to be conceptual.Results also reveal L3 proficiency exerts no influence on conceptual transfer.

Detection method of absence seizures based on Resnet and bidirectional GRU

Background Epilepsy is a common chronic neurological disease.Its repeated seizure attacks have a great negative impact on patients’physical and mental health.The diagnosis of epilepsy mainly depends on electroencephalogram(EEG)signals detection and analysis.There are two main EEG signals detection methods for epilepsy.One is the detection based on abnormal waveform,the other is the analysis of EEG signals based on the traditional machine learning.The feature extraction method of the traditional machine learning is difcult to capture the high-dimension information between adjacent sequences.Methods In this paper,redundant information was removed from the data by Gaussian fltering,downsampling,and short-time Fourier transform.Convolutional Neural Networks(CNN)was used to extract the high-dimensional features of the preprocessed data,and then Gate Recurrent Unit(GRU)was used to combine the sequence information before and after,to fully integrate the adjacent information EEG signals and improve the accuracy of the model detection.Results Four models were designed and compared.The experimental results showed that the prediction model based on deep residual network and bidirectional GRU had the best efect,and the test accuracy of the absence epilepsy test set reached 92%.Conclusions The prediction time of the network is only 10 sec when predicting four-hour EEG signals.It can be efectively used in EEG software to provide reference for doctors in EEG analysis and save doctors’time,which has great practical value.

Preparation and photocatalytic activity of Fe3O4@SiO2@ZnO:La

In this study,Fe3 O4@SiO2@ZnO:La microspheres were successfully prepared.The microspheres have the advantages of both ZnO doped with La and the Fe3 O4@SiO2 structure such that the former improves the photocatalytic activity of ZnO and the latter can be reused.The X-ray diffraction(XRD),a field emission scanning electron microscope(SEM),a field emission transmission electron microscope(TEM),X-ray photoelectron spectroscopy(XPS),and a vibrating sample magnetometer(VSM)were used to characterize Fe3 O4@SiO2@ZnO:La microspheres.Methyl orange was used as the model molecule to study the effect of the Zn2+concentration and the doping amount of La on the photocatalytic activity of Fe3 O4@SiO2@ZnO:La microspheres.Results show that in the synthesis of Fe3 O4@SiO2@ZnO:La microspheres,photocatalytic activity of the microspheres is enhanced first and weakened later with the increase of Zn2+concentration.In the La doping process,the photocatalytic activity of Fe3 O4@SiO2@ZnO:La microspheres is enhanced with the increase in the La doping amount.The magnetic photocatalysts not only have high photocatalytic activity,but also can be reused.After being reused five times,the photocatalyst’s degradation rate of methyl orange is still as high as 81%,which shows that magnetic photocatalysts have prospective wider applications in photocatalytic degradation of dye wastewater.

Sensitive detection of DNA methyltransferase activity based on supercharged fluorescent protein and template-free DNA polymerization

DNA methylation, catalyzed by DNA methyltransferases(MTases), is a key component of genetic regulation, and DNA MTases have been regarded as potential targets in anticancer therapy. Herein, based on our previously developed DNA-mediated supercharged green fluorescent protein(Sc GFP)/graphene oxide(GO) interaction, coupled with methylation-initiated template-free DNA polymerization, we propose a novel fluorescence assay strategy for sensitive detection of DNA MTase activity. A hairpin DNA with a methylation-sensitive site and an amino-modified 3′-terminal(DNA-1) was designed and worked as a starting molecule. In the presence of DNA MTase, methylation-sensitive restriction endonuclease, and terminal deoxynucleotidyl transferase(Td T), DNA-1 can be sequentially methylated, cleaved, and further elongated. The resulting long DNA fragments quickly bind with Sc GFP and form the Sc GFP/DNA nanocomplex. Such nanocomplex can effectively protect Sc GFP from being adsorbed and quenched by GO. Without the methylation-initiated DNA polymerization, the fluorescence of Sc GFP will be quenched by GO. Thus, the DNA MTase activity, which is proportional to the amount of DNA polymerization products, can be measured by reading the fluorescence of Sc GFP/GO. The method was successfully used to detect the activity of DNA adenine methylation(Dam) MTase with a wide linear range(0.1–100 U/m L) and a low detection limit of 0.1 U/m L. In addition, the method showed high selectivity and the potential to be applied in a complex sample. Furthermore, this study was successfully extended to evaluate the inhibition effect of 5-fluorouracil on Dam MTase activity and detect Td T activity.

Catalytic action of rare earth oxide(La_(2)O_(3),CeO_(2),Pr_(6)O_(11))on electrochemical oxidation of activated carbon in molten KOH-NaOH

The oxidation of anode carbon fuel directly affects the electrochemical performance of molten hydroxide direct carbon fuel cell(MHDCFC).In general,the anode carbon fuel can be oxidized at high temperature,thus the direct carbon fuel cell(DCFC)can show great electrochemical performance.In this study,rare earth oxides(La_(2)O_(3),CeO_(2),Pr_(6)O_(11))were prepared by the method of precipitation.Activated carbon was prepared by pretreatment of lignite.Rare earth oxides and activated carbon were mixed as anode carbon fuel,and rare earth oxides were used to catalyze the electrochemical oxidation of anode carbon fuel.The results show that CeO_(2)has better electrocatalytic activity compared with La_(2)O_(3)and Pr_(6)O_(11) in the MHDCFC.The electrochemical test results show that the current density(at 0.4 V)increases from 81.02 to 112.90 mA/cm^(2)and the maximum power density increases from 34.78 to 47.05 mW/cm^(2)at 450℃,when the mass fraction of CeO_(2)is increased from 0 to 40%.When the mass fraction of CeO_(2)is 30%,the current density(82.55 mA/cm^(2)at 0.4 V)at 400℃is higher than that(81.02 mA/cm^(2)at 0.4 V)without CeO_(2)at 450℃.The electrochemical oxidation mechanism of CeO_(2)catalyzed anode carbon fuel is discussed.