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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
Abstract
(
1061
)
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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/(m
2
·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 (
F
v
/
F
m
) of
PCC6715
significantly increased under blue light and decreased significantly under red light; after 6 days of culture, the
F
v
/
F
m
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
Abstract
(
1144
)
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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
Abstract
(
978
)
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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 MgB
2
AN Ling,CHENG Chinping,WANG Bo,ZHUANG Chenggang,LI Xingguo,ZHOU Zengjun,FENG Qingrong
Acta Scientiarum Naturalium Universitatis Pekinensis
Abstract
(
642
)
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The size effect of the raw B powder on the MgB
2
phase formation is studied by the technique of
in-situ
high temperature resistivity (HT-ρT) measurement. The onset temperature,
T
onset
, and the completion temperature,
T
PF
, of the phase formation are determined directly during the ongoing thermal process. These two temperatures,
T
onset
and
T
PF
of the sample synthesized using nanometer B and Mg powders (NanoB-MgB
2
) are 440 and 490℃, respectively, the same as those of the sample using micrometer B and nanometer Mg powders (MicroB-MgB
2
). This indicates that the phase formation temperature of MgB
2
do not depend on the B powder size. The upper limit of the sintering temperature,
T
N
, above which the sample loses superconductivity, is below 750℃ for NanoB-MgB
2
, much lower than 980℃ for the MgB
2
prepared using micron-sized B powder and millimeter sized Mg powder (DM-MgB
2
). In comparison with the sample directly sintered at 650℃<
T
N
, an interesting, irreversible transformation in the crystal structure of the MgB
2
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
Abstract
(
636
)
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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 NH
4
NO
3
or 58.5mmol NaNO
3
. The optimum growth and maximum nitrogenase activity of W11 occurs at the medium containing 10% sucrose and 0.25g/L sodium glutamate, pH5.5, 28-30
o
C. 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
Abstract
(
909
)
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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
15
N Trace Method
LI Xinghong,TIAN Dexiang,YU Zhongju,WANG Yongmin,CHEN Deyuan
Acta Scientiarum Naturalium Universitatis Pekinensis
Abstract
(
806
)
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Reports the determination results of nitrogenase activity of induced cucumber root nudules by
15
N trace method. The root systems bearing induced nodules of cucumber were exposed to a gas mixture containing
15
N
2
for 48h and partial root systems soaked in free-nitrgen culture solution simultaneusly. After exposure the
15
N content in the modulated root systems of cucumber is 0.431 Atom %
15
N by mass spectrometric analysis, whereas in the contrast samples without exposure to
15
N is 0.369 Atom %
15
N. The statiatical t test for the results of
15
N trace experiments is:
t
=3.15 >
t
0.01
=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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