Performance of underwater quantum key distribution with polarization encoding.

Underwater quantum key distribution (QKD) has potential applications in absolutely secure underwater communication. However, the performance of underwater QKD is limited by the optical elements, background light, and dark counts of the detector. In this paper, we propose a modified formula for the quantum bit error rate (QBER), which takes into account the effect of detector efficiency on the QBER caused by the background light. Then we calculate the QBER of the polarization encoding BB84 protocol in Jerlov-type seawater by analyzing the effect of the background light and optical components in a more realistic situation. Finally, we further analyze the final key rate and the maximum secure communication distance in three propagation modes, i.e., upward, downward, and horizontal modes. We find that secure QKD can be performed in the clearest Jerlov-type seawater at a distance of hundreds of meters, even in the worst downward propagation mode. Specifically, by optimizing the system parameters, it is possible to securely transmit information with a rate of 67 kbits/s at a distance of 100 m in the seawater channel with an attenuation coefficient of 0.03/m at night. For practical underwater QKD, the performance can also be improved by using decoy states. Our results are useful for long-distance underwater quantum communication.

[Applications of eco-environmental big data: Progress and prospect]. / 大数据在生态环境领域的应用进展与展望.

With the advance of internet and wireless communication technology, the fields of ecology and environment have entered a new digital era with the amount of data growing explosively and big data technologies attracting more and more attention. The eco-environmental big data is based airborne and space-/land-based observations of ecological and environmental factors and its ultimate goal is to integrate multi-source and multi-scale data for information mining by taking advantages of cloud computation, artificial intelligence, and modeling technologies. In comparison with other fields, the eco-environmental big data has its own characteristics, such as diverse data formats and sources, data collected with various protocols and standards, and serving different clients and organizations with special requirements. Big data technology has been applied worldwide in ecological and environmental fields including global climate prediction, ecological network observation and modeling, and regional air pollution control. The development of eco-environmental big data in China is facing many problems, such as data sharing issues, outdated monitoring facilities and techno-logies, and insufficient data mining capacity. Despite all this, big data technology is critical to solving eco-environmental problems, improving prediction and warning accuracy on eco-environmental catastrophes, and boosting scientific research in the field in China. We expected that the eco-environmental big data would contribute significantly to policy making and environmental services and management, and thus the sustainable development and eco-civilization construction in China in the coming decades.

Channel analysis for single photon underwater free space quantum key distribution.

We investigate the optical absorption and scattering properties of underwater media pertinent to our underwater free space quantum key distribution (QKD) channel model. With the vector radiative transfer theory and Monte Carlo method, we obtain the attenuation of photons, the fidelity of the scattered photons, the quantum bit error rate, and the sifted key generation rate of underwater quantum communication. It can be observed from our simulations that the most secure single photon underwater free space QKD is feasible in the clearest ocean water.

[Study on the chemical constituents of Codonopsis lanceolata].

OBJECTIVE: To study the chemical constituents of Codonopsis lanceolata. METHODS: Chemical constituents were separated with the column chromatographic, and their structures were identified by chemical and spectroscopic methods. RESULTS: Six compounds were isolated and identified as syringin (1), shikimic acid (2), friedelin (3), alpha-spinasterol (4), stigmasterol (5), stigmasta-7-dien-3beta-ol (6). CONCLUSION: Compounds 3-6 are isolated from this plant for the first time.

[Double-mutant dihydrofolate reductase gene transfection into bone marrow cells protects mice from chemotherapy].

OBJECTIVE: To explore the feasibility of transfecting DHFR (human double-mutant dihydrofolate reductase) gene into mouse bone marrow cells and the effect of resistance to high dose MTX chemotherapy. METHODS: After DHFR gene was transfected into mouse bone marrow cells with retroviral vector, the cells were treated with methotrexate (MTX) and then CFU-GM (granulocyte-macrophage colony-forming unit) assay was performed. Peripheral blood leucocytes and platelets, body weight and survival rate were observed. After treatment with high dose MTX, the expression of drug resistance gene was checked by RT-PCR in the transfected bone marrow cells. RESULTS: SFG-F/S-NeoR gene-transfected mice bone marrow cells yielded drug-resistance colonies to MTX (donor mice: 15.8%, recipient mice: 18.0%, control: 0) The peripheral blood leucocytes and platelets, body weight recovered gradually and the survival rate was 83.3% at the 40th day, while 0 in controls in gene transfected mice after large dose MTX treatment. RT-PCR of transgenic mouse marrow cells showed the band of F/S gene (400 bp). CONCLUSION: DHFR gene can not only be integrated and expressed in bone marrow cells but also improve their drug-resistence to MTX.

[Mice transduced with double-mutant dihydrofolate reductase-cytidine deaminase fusion gene attained protection from high dose chemotherapy].

OBJECTIVE: To explore the feasibility of transferring fusion gene of dihydrofolate reductase (DHFR) gene and cytidine deaminase (CD) gene into mouse bone marrow cells in order to observe the drug resistance of high dose methotrexate (MTX) and cytosine arabinoside (Ara-C) in the bone marrow cells and to improve the tolerance of myelosuppression following combination chemotherapy. METHODS: Human double-mutant dihydrofolate reductase-cytidine deaminase fusion gene was transferred into two mice bone marrow cells by retroviral vector. Resistant colony-forming unit granulocyte-macrophage (CFU-GM) assays were performed in mouse bone marrow cells by retroviral infection and after treatment by drugs (Ara-C, MTX, and Ara-C + MTX). DNA was extracted from mouse bone marrow cells. The expression of drug resistant genes in mouse bone marrow cells after transferring by retroviral vector was checked by polymerase chain reaction (PCR). RESULTS: Bone marrow cells after coculture with the retroviral producer cells transduced with the genes (SFG-F/S-CD) showed the drug resistance colonies yield (Colony formation after exposure to Ara-C, MTX and Ara-C + MTX were 56%, 22% and 14%, respectively) and the increase in drug resistant to both MTX and Ara-C (P < 0.005). Expression of DHFR and CD gene in extracted DNA of transfected mice were demonstrated by PCR. CONCLUSIONS: Double drug resistant gene can not only integrate and co-express in mice bone marrow cells but also increase the drug resistance to MTX and Ara-C.