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Effects of Different Light Qualities on the Growth of Thermophilic Cyanobacteria Synechococcus sp. PCC6715
LI Kai, GONG Yiwei, LI Xingkang, ZHANG Yanting, Maurycy Daroch, JIN Peng
Acta Scientiarum Naturalium Universitatis Pekinensis    2020, 56 (4): 739-744.   DOI: 10.13209/j.0479-8023.2020.036
Abstract1061)   HTML    PDF(pc) (864KB)(223)       Save
 In order to understand the lighting quality effects on the light-adaptive growth of cyanobacteria which does not express phycoerythrin, the thermophilic cyanobacteria PCC6715 in logarithmic growth phase was cultured by using white light (control), red light, and blue light with photosynthetically effective photon quantum density (PAR) of 100 μmol/(m2·s). Compared with the growth characteristics of PCC6715 under white light conditions, the changes in the measured and analyzed values of PCC6715 under other light qualities were as follows: the dry weight of PCC6715 significantly increased under blue light and significantly reduced under red light; the red and blue light have different effects on the start time and duration of the photosynthetic pigment synthesis of PCC6715; the maximum light energy conversion efficiency (Fv/Fm) of PCC6715 significantly increased under blue light and decreased significantly under red light; after 6 days of culture, the Fv/Fm of PCC6715 under red and blue light conditions tends to stable. In conclusion, the blue spectrum lighting promotes the growth of PCC6715, while red light inhibits the growth of PCC6715. At the same time, PCC6715 produces light-adaptive growth under both red and blue light, the reduction of phycocyanin content caused light-adaptive growth of PCC6715 in red light, and the light-adaptive growth of PCC6715 in blue light was due to the increase of phycocyanin content.
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Distant Supervision for Relation Extraction with Gate Mechanism
LI Xingya, CHEN Yufeng, XU Jin’an, ZHANG Yujie
Acta Scientiarum Naturalium Universitatis Pekinensis    2020, 56 (1): 39-44.   DOI: 10.13209/j.0479-8023.2019.101
Abstract1144)   HTML    PDF(pc) (699KB)(164)       Save
A piecewise convolutional neural network with gating mechanism is proposed, which would automatically filter positive correlation features at word-level. Moreover, the idea of soft-label is introduced to the gating mechanism to weaken the impact of hard labels on noise filtering. Combined with sentence-level noise filtering, the overall performance of the model is improved. The experimental results on the public dataset show that the proposed model has a significant improvement compared to the sentence-level noise filtering methods. 
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Influence of Air on the Performance of InAs Nanowire FET
ZHANG Xintong;LI Xing;WANG Xiaoye;FU Mengqi;YANG Tao;CHEN Qing
   2015, 51 (4): 585-590.   DOI: 10.13209/j.0479-8023.2015.013
Abstract978)      PDF(pc) (3920KB)(446)       Save
Planar field effect transistor nanodevices were fabricated based on individual InAs nanowires. The electrical performance of the devices was measured and studied in vacuum, air, N2, O2, H2O and pollutant in air, NO2. Compared with the performance in vacuum, the performance of the device in air changes, e.g. the threshold voltage of the device (VT) shifts to positive direction, the off-state current (Ioff) increases and the on-off ratio (Ion/Ioff) decreases in air. The main air component, N2, does not have distinguishable impact on the performance of the device. The effect of O2 is very weak. H2O increases Ioff, decreases Ion/Ioff and shifts VT negatively. The component of the pollutant in air, NO2 is found to bring a positive shift of VT, and an unchanged Ion/Ioff.
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Effect of Nanometer-Sized B Powder on Phase Formation of Polycrystalline MgB2
AN Ling,CHENG Chinping,WANG Bo,ZHUANG Chenggang,LI Xingguo,ZHOU Zengjun,FENG Qingrong
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract642)            Save
The size effect of the raw B powder on the MgB2 phase formation is studied by the technique of in-situ high temperature resistivity (HT-ρT) measurement. The onset temperature, Tonset, and the completion temperature, TPF, of the phase formation are determined directly during the ongoing thermal process. These two temperatures, Tonset and TPF of the sample synthesized using nanometer B and Mg powders (NanoB-MgB2) are 440 and 490℃, respectively, the same as those of the sample using micrometer B and nanometer Mg powders (MicroB-MgB2). This indicates that the phase formation temperature of MgB2 do not depend on the B powder size. The upper limit of the sintering temperature, TN, above which the sample loses superconductivity, is below 750℃ for NanoB-MgB2, much lower than 980℃ for the MgB2 prepared using micron-sized B powder and millimeter sized Mg powder (DM-MgB2). In comparison with the sample directly sintered at 650℃<TN, an interesting, irreversible transformation in the crystal structure of the MgB2 phase is observed with the sample going through the stages of initial sintering at 750℃, then re-sintering at 650℃ in an Mg-rich environment after the processes of regrinding and pressing.
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Study on A Nitrogen-Fixing Pantoea Agglomeras Isolated from the Root of Sugar Cane
LI Xinghong,LI Dachei,LI Wei,PENG Lie
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract636)            Save
A strain of nitrogen-fixing bacteria, W11, isolated from the root of sugar cane has been identificated as Pantoea agglomeras using an auto-identificat ion system for bacterium based on 96 biochemical test data. W11 has the properties of tolerance to acid(pH3.5) and high sucrose concentration (30%), A amount of acid was formed and reduced the acidity of medium to pH of 4.41, the nitrogenase activity was inhibited in presence of 3.1mmol NH4NO3 or 58.5mmol NaNO3. The optimum growth and maximum nitrogenase activity of W11 occurs at the medium containing 10% sucrose and 0.25g/L sodium glutamate, pH5.5, 28-30oC. Its behaviours of tolerance to acid and high sucrose concentration, acid production and the use of carbon substrates is simiiar to that the Acetobacter diazotrophicus has. The strain W11 was inferred to have a nitrogen-fixing relationship associated with the root of sugar cane.
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Optimization Calculation of the Roof Thickness for 15MeV X-Ray Linear Accelerator
LI Xinghong
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract909)            Save
Presents a methods for calculation of the thickness of a concrete roof for shielding the angularity distributed X-ray radiation produced by a L-6000HRO 15MeV X-ray Linear Accelerator. The required roof thickness was found to be 31cm in order to ensure the dose equivalent rate to be 0.0025mSv. h-1 at an observation point 20 m away from the machine. This radiation comes mainly from skyshine. The thickness of that concrete roof was further optimized and found to be 50 cm. The dosimetric measurements made after the accelerator building had constructed showed that the shielding design was safe and econonic, and the skyshine radiation had been decreased to a level as low as reasonably achievable.
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Determination of Nitrogenase Activity of Induced Cucumber Nodules by 15N Trace Method
LI Xinghong,TIAN Dexiang,YU Zhongju,WANG Yongmin,CHEN Deyuan
Acta Scientiarum Naturalium Universitatis Pekinensis   
Abstract806)            Save
Reports the determination results of nitrogenase activity of induced cucumber root nudules by 15N trace method. The root systems bearing induced nodules of cucumber were exposed to a gas mixture containing 15N2 for 48h and partial root systems soaked in free-nitrgen culture solution simultaneusly. After exposure the 15N content in the modulated root systems of cucumber is 0.431 Atom % 15N by mass spectrometric analysis, whereas in the contrast samples without exposure to 15N is 0.369 Atom % 15N. The statiatical t test for the results of 15N trace experiments is: t=3.15 > t0.01=2.819, It has been demonstrated that the nitrogenase activity in cucumber nudules is at a remarkable level of 99.9%. The nitrogenase activity in detached nodules of cucumber was also determined by conventional acetylene reduction method. In both methods clear evidences of nitrogenase activity were obtained for the induced nodules of cucumber.
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